diff --git a/maps/treebidimap/enumerable.go b/maps/treebidimap/enumerable.go
index d5d829a..6ac702b 100644
--- a/maps/treebidimap/enumerable.go
+++ b/maps/treebidimap/enumerable.go
@@ -21,7 +21,7 @@ func (m *Map) Each(f func(key interface{}, value interface{})) {
 // Map invokes the given function once for each element and returns a container
 // containing the values returned by the given function as key/value pairs.
 func (m *Map) Map(f func(key1 interface{}, value1 interface{}) (interface{}, interface{})) *Map {
-	newMap := NewWith(m.keyComparator, m.valueComparator)
+	newMap := NewWithTrees(m.forwardMap.New(), m.inverseMap.New())
 	iterator := m.Iterator()
 	for iterator.Next() {
 		key2, value2 := f(iterator.Key(), iterator.Value())
@@ -32,7 +32,7 @@ func (m *Map) Map(f func(key1 interface{}, value1 interface{}) (interface{}, int
 
 // Select returns a new container containing all elements for which the given function returns a true value.
 func (m *Map) Select(f func(key interface{}, value interface{}) bool) *Map {
-	newMap := NewWith(m.keyComparator, m.valueComparator)
+	newMap := NewWithTrees(m.forwardMap.New(), m.inverseMap.New())
 	iterator := m.Iterator()
 	for iterator.Next() {
 		if f(iterator.Key(), iterator.Value()) {
diff --git a/maps/treebidimap/iterator.go b/maps/treebidimap/iterator.go
index af9e27a..8329591 100644
--- a/maps/treebidimap/iterator.go
+++ b/maps/treebidimap/iterator.go
@@ -4,10 +4,7 @@
 
 package treebidimap
 
-import (
-	"github.com/emirpasic/gods/containers"
-	rbt "github.com/emirpasic/gods/trees/redblacktree"
-)
+import "github.com/emirpasic/gods/containers"
 
 func assertIteratorImplementation() {
 	var _ containers.ReverseIteratorWithKey = (*Iterator)(nil)
@@ -15,7 +12,7 @@ func assertIteratorImplementation() {
 
 // Iterator holding the iterator's state
 type Iterator struct {
-	iterator rbt.Iterator
+	iterator containers.ReverseIteratorWithKey
 }
 
 // Iterator returns a stateful iterator whose elements are key/value pairs.
diff --git a/maps/treebidimap/treebidimap.go b/maps/treebidimap/treebidimap.go
index 87eff9f..4812de6 100644
--- a/maps/treebidimap/treebidimap.go
+++ b/maps/treebidimap/treebidimap.go
@@ -19,10 +19,12 @@ package treebidimap
 
 import (
 	"fmt"
+	"strings"
+
 	"github.com/emirpasic/gods/maps"
-	"github.com/emirpasic/gods/trees/redblacktree"
 	"github.com/emirpasic/gods/utils"
-	"strings"
+	"github.com/spewspews/gods/trees"
+	"github.com/spewspews/gods/trees/redblacktree"
 )
 
 func assertMapImplementation() {
@@ -31,10 +33,8 @@ func assertMapImplementation() {
 
 // Map holds the elements in two red-black trees.
 type Map struct {
-	forwardMap      redblacktree.Tree
-	inverseMap      redblacktree.Tree
-	keyComparator   utils.Comparator
-	valueComparator utils.Comparator
+	forwardMap      trees.Tree
+	inverseMap      trees.Tree
 }
 
 type data struct {
@@ -45,10 +45,8 @@ type data struct {
 // NewWith instantiates a bidirectional map.
 func NewWith(keyComparator utils.Comparator, valueComparator utils.Comparator) *Map {
 	return &Map{
-		forwardMap:      *redblacktree.NewWith(keyComparator),
-		inverseMap:      *redblacktree.NewWith(valueComparator),
-		keyComparator:   keyComparator,
-		valueComparator: valueComparator,
+		forwardMap: redblacktree.NewWith(keyComparator),
+		inverseMap: redblacktree.NewWith(valueComparator),
 	}
 }
 
@@ -62,6 +60,10 @@ func NewWithStringComparators() *Map {
 	return NewWith(utils.StringComparator, utils.StringComparator)
 }
 
+func NewWithTrees(forwardTree trees.Tree, inverseTree trees.Tree) *Map {
+	return &Map{forwardMap: forwardTree, inverseMap: inverseTree}
+}
+
 // Put inserts element into the map.
 func (m *Map) Put(key interface{}, value interface{}) {
 	if d, ok := m.forwardMap.Get(key); ok {
diff --git a/maps/treemap/enumerable.go b/maps/treemap/enumerable.go
index 8cea6d0..5f66ffb 100644
--- a/maps/treemap/enumerable.go
+++ b/maps/treemap/enumerable.go
@@ -4,10 +4,7 @@
 
 package treemap
 
-import (
-	"github.com/emirpasic/gods/containers"
-	rbt "github.com/emirpasic/gods/trees/redblacktree"
-)
+import "github.com/emirpasic/gods/containers"
 
 func assertEnumerableImplementation() {
 	var _ containers.EnumerableWithKey = (*Map)(nil)
@@ -24,7 +21,7 @@ func (m *Map) Each(f func(key interface{}, value interface{})) {
 // Map invokes the given function once for each element and returns a container
 // containing the values returned by the given function as key/value pairs.
 func (m *Map) Map(f func(key1 interface{}, value1 interface{}) (interface{}, interface{})) *Map {
-	newMap := &Map{tree: rbt.NewWith(m.tree.Comparator)}
+	newMap := &Map{tree: m.tree.New()}
 	iterator := m.Iterator()
 	for iterator.Next() {
 		key2, value2 := f(iterator.Key(), iterator.Value())
@@ -35,7 +32,7 @@ func (m *Map) Map(f func(key1 interface{}, value1 interface{}) (interface{}, int
 
 // Select returns a new container containing all elements for which the given function returns a true value.
 func (m *Map) Select(f func(key interface{}, value interface{}) bool) *Map {
-	newMap := &Map{tree: rbt.NewWith(m.tree.Comparator)}
+	newMap := &Map{tree: m.tree.New()}
 	iterator := m.Iterator()
 	for iterator.Next() {
 		if f(iterator.Key(), iterator.Value()) {
diff --git a/maps/treemap/iterator.go b/maps/treemap/iterator.go
index 02b5c75..3de1482 100644
--- a/maps/treemap/iterator.go
+++ b/maps/treemap/iterator.go
@@ -4,10 +4,7 @@
 
 package treemap
 
-import (
-	"github.com/emirpasic/gods/containers"
-	rbt "github.com/emirpasic/gods/trees/redblacktree"
-)
+import "github.com/emirpasic/gods/containers"
 
 func assertIteratorImplementation() {
 	var _ containers.ReverseIteratorWithKey = (*Iterator)(nil)
@@ -15,7 +12,7 @@ func assertIteratorImplementation() {
 
 // Iterator holding the iterator's state
 type Iterator struct {
-	iterator rbt.Iterator
+	iterator containers.ReverseIteratorWithKey
 }
 
 // Iterator returns a stateful iterator whose elements are key/value pairs.
diff --git a/maps/treemap/treemap.go b/maps/treemap/treemap.go
index a1e58ad..bf62197 100644
--- a/maps/treemap/treemap.go
+++ b/maps/treemap/treemap.go
@@ -14,7 +14,8 @@ package treemap
 import (
 	"fmt"
 	"github.com/emirpasic/gods/maps"
-	rbt "github.com/emirpasic/gods/trees/redblacktree"
+	rbt "github.com/spewspews/gods/trees/redblacktree"
+	"github.com/spewspews/gods/trees"
 	"github.com/emirpasic/gods/utils"
 	"strings"
 )
@@ -25,7 +26,7 @@ func assertMapImplementation() {
 
 // Map holds the elements in a red-black tree
 type Map struct {
-	tree *rbt.Tree
+	tree trees.Tree
 }
 
 // NewWith instantiates a tree map with the custom comparator.
@@ -43,6 +44,11 @@ func NewWithStringComparator() *Map {
 	return &Map{tree: rbt.NewWithStringComparator()}
 }
 
+// NewWithTree instantiates a new empty map with given tree
+func NewWithTree(tree trees.Tree) *Map {
+	return &Map{tree: tree}
+}
+
 // Put inserts key-value pair into the map.
 // Key should adhere to the comparator's type assertion, otherwise method panics.
 func (m *Map) Put(key interface{}, value interface{}) {
@@ -90,19 +96,13 @@ func (m *Map) Clear() {
 // Min returns the minimum key and its value from the tree map.
 // Returns nil, nil if map is empty.
 func (m *Map) Min() (key interface{}, value interface{}) {
-	if node := m.tree.Left(); node != nil {
-		return node.Key, node.Value
-	}
-	return nil, nil
+	return m.tree.Min()
 }
 
 // Max returns the maximum key and its value from the tree map.
 // Returns nil, nil if map is empty.
 func (m *Map) Max() (key interface{}, value interface{}) {
-	if node := m.tree.Right(); node != nil {
-		return node.Key, node.Value
-	}
-	return nil, nil
+	return m.tree.Max()
 }
 
 // String returns a string representation of container
diff --git a/maps/treemap/treemap_test.go b/maps/treemap/treemap_test.go
index 0039601..4aa3e5e 100644
--- a/maps/treemap/treemap_test.go
+++ b/maps/treemap/treemap_test.go
@@ -7,6 +7,8 @@ package treemap
 import (
 	"fmt"
 	"testing"
+
+	"github.com/spewspews/gods/trees/avltree"
 )
 
 func TestMapPut(t *testing.T) {
@@ -51,6 +53,48 @@ func TestMapPut(t *testing.T) {
 	}
 }
 
+func TestMapAVLPut(t *testing.T) {
+	m := NewWithTree(avltree.NewWithIntComparator())
+	m.Put(5, "e")
+	m.Put(6, "f")
+	m.Put(7, "g")
+	m.Put(3, "c")
+	m.Put(4, "d")
+	m.Put(1, "x")
+	m.Put(2, "b")
+	m.Put(1, "a") //overwrite
+
+	if actualValue := m.Size(); actualValue != 7 {
+		t.Errorf("Got %v expected %v", actualValue, 7)
+	}
+	if actualValue, expectedValue := m.Keys(), []interface{}{1, 2, 3, 4, 5, 6, 7}; !sameElements(actualValue, expectedValue) {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if actualValue, expectedValue := m.Values(), []interface{}{"a", "b", "c", "d", "e", "f", "g"}; !sameElements(actualValue, expectedValue) {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+
+	// key,expectedValue,expectedFound
+	tests1 := [][]interface{}{
+		{1, "a", true},
+		{2, "b", true},
+		{3, "c", true},
+		{4, "d", true},
+		{5, "e", true},
+		{6, "f", true},
+		{7, "g", true},
+		{8, nil, false},
+	}
+
+	for _, test := range tests1 {
+		// retrievals
+		actualValue, actualFound := m.Get(test[0])
+		if actualValue != test[1] || actualFound != test[2] {
+			t.Errorf("Got %v expected %v", actualValue, test[1])
+		}
+	}
+
+}
 func TestMapRemove(t *testing.T) {
 	m := NewWithIntComparator()
 	m.Put(5, "e")
diff --git a/sets/treeset/enumerable.go b/sets/treeset/enumerable.go
index 59a0913..9a3cb62 100644
--- a/sets/treeset/enumerable.go
+++ b/sets/treeset/enumerable.go
@@ -4,10 +4,7 @@
 
 package treeset
 
-import (
-	"github.com/emirpasic/gods/containers"
-	rbt "github.com/emirpasic/gods/trees/redblacktree"
-)
+import "github.com/emirpasic/gods/containers"
 
 func assertEnumerableImplementation() {
 	var _ containers.EnumerableWithIndex = (*Set)(nil)
@@ -24,7 +21,7 @@ func (set *Set) Each(f func(index int, value interface{})) {
 // Map invokes the given function once for each element and returns a
 // container containing the values returned by the given function.
 func (set *Set) Map(f func(index int, value interface{}) interface{}) *Set {
-	newSet := &Set{tree: rbt.NewWith(set.tree.Comparator)}
+	newSet := &Set{tree: set.tree.New()}
 	iterator := set.Iterator()
 	for iterator.Next() {
 		newSet.Add(f(iterator.Index(), iterator.Value()))
@@ -34,7 +31,7 @@ func (set *Set) Map(f func(index int, value interface{}) interface{}) *Set {
 
 // Select returns a new container containing all elements for which the given function returns a true value.
 func (set *Set) Select(f func(index int, value interface{}) bool) *Set {
-	newSet := &Set{tree: rbt.NewWith(set.tree.Comparator)}
+	newSet := NewWithTree(set.tree.New())
 	iterator := set.Iterator()
 	for iterator.Next() {
 		if f(iterator.Index(), iterator.Value()) {
diff --git a/sets/treeset/iterator.go b/sets/treeset/iterator.go
index 2cb465f..9f76f66 100644
--- a/sets/treeset/iterator.go
+++ b/sets/treeset/iterator.go
@@ -6,7 +6,7 @@ package treeset
 
 import (
 	"github.com/emirpasic/gods/containers"
-	rbt "github.com/emirpasic/gods/trees/redblacktree"
+	"github.com/spewspews/gods/trees"
 )
 
 func assertIteratorImplementation() {
@@ -16,8 +16,8 @@ func assertIteratorImplementation() {
 // Iterator returns a stateful iterator whose values can be fetched by an index.
 type Iterator struct {
 	index    int
-	iterator rbt.Iterator
-	tree     *rbt.Tree
+	iterator containers.ReverseIteratorWithKey
+	tree     trees.Tree
 }
 
 // Iterator holding the iterator's state
diff --git a/sets/treeset/treeset.go b/sets/treeset/treeset.go
index 9ead634..ee56cc5 100644
--- a/sets/treeset/treeset.go
+++ b/sets/treeset/treeset.go
@@ -11,10 +11,12 @@ package treeset
 
 import (
 	"fmt"
+	"strings"
+
 	"github.com/emirpasic/gods/sets"
-	rbt "github.com/emirpasic/gods/trees/redblacktree"
 	"github.com/emirpasic/gods/utils"
-	"strings"
+	"github.com/spewspews/gods/trees"
+	rbt "github.com/spewspews/gods/trees/redblacktree"
 )
 
 func assertSetImplementation() {
@@ -23,7 +25,7 @@ func assertSetImplementation() {
 
 // Set holds elements in a red-black tree
 type Set struct {
-	tree *rbt.Tree
+	tree trees.Tree
 }
 
 var itemExists = struct{}{}
@@ -43,6 +45,11 @@ func NewWithStringComparator() *Set {
 	return &Set{tree: rbt.NewWithStringComparator()}
 }
 
+// NewWithTree instantiates a new empty set with given tree
+func NewWithTree(tree trees.Tree) *Set {
+	return &Set{tree: tree}
+}
+
 // Add adds the items (one or more) to the set.
 func (set *Set) Add(items ...interface{}) {
 	for _, item := range items {
diff --git a/sets/treeset/treeset_test.go b/sets/treeset/treeset_test.go
index 881adc2..e5d5c1e 100644
--- a/sets/treeset/treeset_test.go
+++ b/sets/treeset/treeset_test.go
@@ -7,6 +7,8 @@ package treeset
 import (
 	"fmt"
 	"testing"
+
+	"github.com/spewspews/gods/trees/avltree"
 )
 
 func TestSetAdd(t *testing.T) {
@@ -27,6 +29,24 @@ func TestSetAdd(t *testing.T) {
 	}
 }
 
+func TestSetAVLAdd(t *testing.T) {
+	set := NewWithTree(avltree.NewWithIntComparator())
+	set.Add()
+	set.Add(1)
+	set.Add(2)
+	set.Add(2, 3)
+	set.Add()
+	if actualValue := set.Empty(); actualValue != false {
+		t.Errorf("Got %v expected %v", actualValue, false)
+	}
+	if actualValue := set.Size(); actualValue != 3 {
+		t.Errorf("Got %v expected %v", actualValue, 3)
+	}
+	if actualValue, expectedValue := fmt.Sprintf("%d%d%d", set.Values()...), "123"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+}
+
 func TestSetContains(t *testing.T) {
 	set := NewWithIntComparator()
 	set.Add(3, 1, 2)
diff --git a/trees/avltree/LICENSE b/trees/avltree/LICENSE
new file mode 100644
index 0000000..985d32d
--- /dev/null
+++ b/trees/avltree/LICENSE
@@ -0,0 +1,13 @@
+Copyright (c) 2017 Benjamin Scher Purcell <benjapurcell@gmail.com>
+
+Permission to use, copy, modify, and distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
diff --git a/trees/avltree/avltree.go b/trees/avltree/avltree.go
new file mode 100644
index 0000000..fe9cf40
--- /dev/null
+++ b/trees/avltree/avltree.go
@@ -0,0 +1,493 @@
+// Copyright (c) 2017, Benjamin Scher Purcell. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package avltree implements an AVL balanced binary tree.
+//
+// Structure is not thread safe.
+package avltree
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+
+	"github.com/emirpasic/gods/utils"
+	"github.com/spewspews/gods/trees"
+)
+
+func assertTreeImplementation() {
+	var _ trees.Tree = new(Tree)
+}
+
+var dbgLog = log.New(ioutil.Discard, "avltree: ", log.LstdFlags)
+
+// Tree holds elements of the AVL tree.
+type Tree struct {
+	Root       *Node
+	size       int
+	comparator utils.Comparator
+}
+
+// Node is a single element within the tree
+type Node struct {
+	Key   interface{}
+	Value interface{}
+	c     [2]*Node
+	p     *Node
+	b     int8
+}
+
+// NewWith instantiates an AVL tree with the custom comparator.
+func NewWith(comparator utils.Comparator) *Tree {
+	return &Tree{comparator: comparator}
+}
+
+// NewWithIntComparator instantiates an AVL tree with the IntComparator, i.e. keys are of type int.
+func NewWithIntComparator() *Tree {
+	return &Tree{comparator: utils.IntComparator}
+}
+
+// NewWithStringComparator instantiates an AVL tree with the StringComparator, i.e. keys are of type string.
+func NewWithStringComparator() *Tree {
+	return &Tree{comparator: utils.StringComparator}
+}
+
+// Comparator returns the comparator function for the tree.
+func (t *Tree) Comparator() utils.Comparator {
+	return t.comparator
+}
+
+// New returns a new empty tree with the same comparator.
+func (t *Tree) New() trees.Tree {
+	return &Tree{comparator: t.comparator}
+}
+
+// Size returns the number of elements stored in the tree.
+func (t *Tree) Size() int {
+	return t.size
+}
+
+// Empty returns true if tree does not contain any nodes.
+func (t *Tree) Empty() bool {
+	return t.size == 0
+}
+
+// Clear removes all nodes from the tree.
+func (t *Tree) Clear() {
+	t.Root = nil
+	t.size = 0
+}
+
+// Get searches the node in the tree by key and returns its value or nil if key is not found in tree.
+// Second return parameter is true if key was found, otherwise false.
+// Key should adhere to the comparator's type assertion, otherwise method panics.
+func (t *Tree) Get(key interface{}) (value interface{}, found bool) {
+	n := t.Root
+	for n != nil {
+		cmp := t.comparator(key, n.Key)
+		switch {
+		case cmp == 0:
+			return n.Value, true
+		case cmp < 0:
+			n = n.c[0]
+		case cmp > 0:
+			n = n.c[1]
+		}
+	}
+	return nil, false
+}
+
+// Floor Finds floor node of the input key, return the floor node or nil if no ceiling is found.
+// Second return parameter is true if floor was found, otherwise false.
+//
+// Floor node is defined as the largest node that is smaller than or equal to the given node.
+// A floor node may not be found, either because the tree is empty, or because
+// all nodes in the tree is larger than the given node.
+//
+// Key should adhere to the comparator's type assertion, otherwise method panics.
+func (t *Tree) Floor(key interface{}) (floor *Node, found bool) {
+	found = false
+	n := t.Root
+	for n != nil {
+		c := t.comparator(key, n.Key)
+		switch {
+		case c == 0:
+			return n, true
+		case c < 0:
+			n = n.c[0]
+		case c > 0:
+			floor, found = n, true
+			n = n.c[1]
+		}
+	}
+	if found {
+		return
+	}
+	return nil, false
+}
+
+// Ceiling finds ceiling node of the input key, return the ceiling node or nil if no ceiling is found.
+// Second return parameter is true if ceiling was found, otherwise false.
+//
+// Ceiling node is defined as the smallest node that is larger than or equal to the given node.
+// A ceiling node may not be found, either because the tree is empty, or because
+// all nodes in the tree is smaller than the given node.
+//
+// Key should adhere to the comparator's type assertion, otherwise method panics.
+func (t *Tree) Ceiling(key interface{}) (floor *Node, found bool) {
+	found = false
+	n := t.Root
+	for n != nil {
+		c := t.comparator(key, n.Key)
+		switch {
+		case c == 0:
+			return n, true
+		case c < 0:
+			floor, found = n, true
+			n = n.c[0]
+		case c > 0:
+			n = n.c[1]
+		}
+	}
+	if found {
+		return
+	}
+	return nil, false
+}
+
+// Put inserts node into the tree.
+// Key should adhere to the comparator's type assertion, otherwise method panics.
+func (t *Tree) Put(key interface{}, value interface{}) {
+	var put func(*Node, **Node) bool
+	put = func(p *Node, qp **Node) bool {
+		q := *qp
+		if q == nil {
+			t.size++
+			*qp = &Node{Key: key, Value: value, p: p}
+			return true
+		}
+
+		c := t.comparator(key, q.Key)
+		if c == 0 {
+			q.Key = key
+			q.Value = value
+			return false
+		}
+
+		if c < 0 {
+			c = -1
+		} else {
+			c = 1
+		}
+		a := (c + 1) / 2
+		var fix bool
+		fix = put(q, &q.c[a])
+		if fix {
+			return putFix(int8(c), qp)
+		}
+		return false
+	}
+
+	put(nil, &t.Root)
+}
+
+// Remove remove the node from the tree by key.
+// Key should adhere to the comparator's type assertion, otherwise method panics.
+func (t *Tree) Remove(key interface{}) {
+	var remove func(**Node) bool
+	remove = func(qp **Node) bool {
+		q := *qp
+		if q == nil {
+			return false
+		}
+
+		c := t.comparator(key, q.Key)
+		if c == 0 {
+			t.size--
+			if q.c[1] == nil {
+				if q.c[0] != nil {
+					q.c[0].p = q.p
+				}
+				*qp = q.c[0]
+				return true
+			}
+			fix := removeMin(&q.c[1], &q.Key, &q.Value)
+			if fix {
+				return removeFix(-1, qp)
+			}
+			return false
+		}
+
+		if c < 0 {
+			c = -1
+		} else {
+			c = 1
+		}
+		a := (c + 1) / 2
+		fix := remove(&q.c[a])
+		if fix {
+			return removeFix(int8(-c), qp)
+		}
+		return false
+	}
+
+	remove(&t.Root)
+}
+
+func removeMin(qp **Node, minKey *interface{}, minVal *interface{}) bool {
+	q := *qp
+	if q.c[0] == nil {
+		*minKey = q.Key
+		*minVal = q.Value
+		if q.c[1] != nil {
+			q.c[1].p = q.p
+		}
+		*qp = q.c[1]
+		return true
+	}
+	fix := removeMin(&q.c[0], minKey, minVal)
+	if fix {
+		return removeFix(1, qp)
+	}
+	return false
+}
+
+func putFix(c int8, t **Node) bool {
+	s := *t
+	if s.b == 0 {
+		s.b = c
+		return true
+	}
+
+	if s.b == -c {
+		s.b = 0
+		return false
+	}
+
+	if s.c[(c+1)/2].b == c {
+		s = singlerot(c, s)
+	} else {
+		s = doublerot(c, s)
+	}
+	*t = s
+	return false
+}
+
+func removeFix(c int8, t **Node) bool {
+	s := *t
+	if s.b == 0 {
+		s.b = c
+		return false
+	}
+
+	if s.b == -c {
+		s.b = 0
+		return true
+	}
+
+	a := (c + 1) / 2
+	if s.c[a].b == 0 {
+		s = rotate(c, s)
+		s.b = -c
+		*t = s
+		return false
+	}
+
+	if s.c[a].b == c {
+		s = singlerot(c, s)
+	} else {
+		s = doublerot(c, s)
+	}
+	*t = s
+	return true
+}
+
+func singlerot(c int8, s *Node) *Node {
+	dbgLog.Printf("singlerot: enter %p:%v %d\n", s, s, c)
+	s.b = 0
+	s = rotate(c, s)
+	s.b = 0
+	dbgLog.Printf("singlerot: exit %p:%v\n", s, s)
+	return s
+}
+
+func doublerot(c int8, s *Node) *Node {
+	dbgLog.Printf("doublerot: enter %p:%v %d\n", s, s, c)
+	a := (c + 1) / 2
+	r := s.c[a]
+	s.c[a] = rotate(-c, s.c[a])
+	p := rotate(c, s)
+	if r.p != p || s.p != p {
+		panic("doublerot: bad parents")
+	}
+
+	switch {
+	default:
+		s.b = 0
+		r.b = 0
+	case p.b == c:
+		s.b = -c
+		r.b = 0
+	case p.b == -c:
+		s.b = 0
+		r.b = c
+	}
+
+	p.b = 0
+	dbgLog.Printf("doublerot: exit %p:%v\n", s, s)
+	return p
+}
+
+func rotate(c int8, s *Node) *Node {
+	dbgLog.Printf("rotate: enter %p:%v %d\n", s, s, c)
+	a := (c + 1) / 2
+	r := s.c[a]
+	s.c[a] = r.c[a^1]
+	if s.c[a] != nil {
+		s.c[a].p = s
+	}
+	r.c[a^1] = s
+	r.p = s.p
+	s.p = r
+	dbgLog.Printf("rotate: exit %p:%v\n", r, r)
+	return r
+}
+
+// Keys returns all keys in-order
+func (t *Tree) Keys() []interface{} {
+	keys := make([]interface{}, t.size)
+	it := t.Iterator()
+	for i := 0; it.Next(); i++ {
+		keys[i] = it.Key()
+	}
+	return keys
+}
+
+// Values returns all values in-order based on the key.
+func (t *Tree) Values() []interface{} {
+	values := make([]interface{}, t.size)
+	it := t.Iterator()
+	for i := 0; it.Next(); i++ {
+		values[i] = it.Value()
+	}
+	return values
+}
+
+// Left returns the minimum element of the AVL tree
+// or nil if the tree is empty.
+func (t *Tree) Left() *Node {
+	return t.bottom(0)
+}
+
+// Right returns the maximum element of the AVL tree
+// or nil if the tree is empty.
+func (t *Tree) Right() *Node {
+	return t.bottom(1)
+}
+
+// Min returns the minimum key value pair of the AVL tree
+// or nils if the tree is empty.
+func (t *Tree) Min() (interface{}, interface{}) {
+	n := t.bottom(0)
+	if n == nil {
+		return nil, nil
+	}
+	return n.Key, n.Value
+}
+
+// Max returns the minimum key value pair of the AVL tree
+// or nils if the tree is empty.
+func (t *Tree) Max() (interface{}, interface{}) {
+	n := t.bottom(1)
+	if n == nil {
+		return nil, nil
+	}
+	return n.Key, n.Value
+}
+
+func (t *Tree) bottom(d int) *Node {
+	n := t.Root
+	if n == nil {
+		return nil
+	}
+
+	for c := n.c[d]; c != nil; c = n.c[d] {
+		n = c
+	}
+	return n
+}
+
+// Prev returns the previous element in an inorder
+// walk of the AVL tree.
+func (n *Node) Prev() *Node {
+	return n.walk1(0)
+}
+
+// Next returns the next element in an inorder
+// walk of the AVL tree.
+func (n *Node) Next() *Node {
+	return n.walk1(1)
+}
+
+func (n *Node) walk1(a int) *Node {
+	if n == nil {
+		return nil
+	}
+
+	if n.c[a] != nil {
+		n = n.c[a]
+		for n.c[a^1] != nil {
+			n = n.c[a^1]
+		}
+		return n
+	}
+
+	p := n.p
+	for p != nil && p.c[a] == n {
+		n = p
+		p = p.p
+	}
+	return p
+}
+
+// String returns a string representation of container
+func (t *Tree) String() string {
+	str := "AVLTree\n"
+	if !t.Empty() {
+		output(t.Root, "", true, &str)
+	}
+	return str
+}
+
+func (n *Node) String() string {
+	return fmt.Sprintf("%v", n.Key)
+}
+
+func output(node *Node, prefix string, isTail bool, str *string) {
+	if node.c[0] != nil {
+		newPrefix := prefix
+		if isTail {
+			newPrefix += "│   "
+		} else {
+			newPrefix += "    "
+		}
+		output(node.c[0], newPrefix, false, str)
+	}
+	*str += prefix
+	if isTail {
+		*str += "└── "
+	} else {
+		*str += "┌── "
+	}
+	*str += node.String() + "\n"
+	if node.c[1] != nil {
+		newPrefix := prefix
+		if isTail {
+			newPrefix += "    "
+		} else {
+			newPrefix += "│   "
+		}
+		output(node.c[1], newPrefix, true, str)
+	}
+}
diff --git a/trees/avltree/avltree_test.go b/trees/avltree/avltree_test.go
new file mode 100644
index 0000000..2e72db3
--- /dev/null
+++ b/trees/avltree/avltree_test.go
@@ -0,0 +1,700 @@
+// Copyright (c) 2017, Benjamin Scher Purcell. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package avltree
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestAVLTreePut(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(5, "e")
+	tree.Put(6, "f")
+	tree.Put(7, "g")
+	tree.Put(3, "c")
+	tree.Put(4, "d")
+	tree.Put(1, "x")
+	tree.Put(2, "b")
+	tree.Put(1, "a") //overwrite
+
+	if actualValue := tree.Size(); actualValue != 7 {
+		t.Errorf("Got %v expected %v", actualValue, 7)
+	}
+	if actualValue, expectedValue := fmt.Sprintf("%d%d%d%d%d%d%d", tree.Keys()...), "1234567"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if actualValue, expectedValue := fmt.Sprintf("%s%s%s%s%s%s%s", tree.Values()...), "abcdefg"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+
+	tests1 := [][]interface{}{
+		{1, "a", true},
+		{2, "b", true},
+		{3, "c", true},
+		{4, "d", true},
+		{5, "e", true},
+		{6, "f", true},
+		{7, "g", true},
+		{8, nil, false},
+	}
+
+	for _, test := range tests1 {
+		// retrievals
+		actualValue, actualFound := tree.Get(test[0])
+		if actualValue != test[1] || actualFound != test[2] {
+			t.Errorf("Got %v expected %v", actualValue, test[1])
+		}
+	}
+}
+
+func TestAVLTreeRemove(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(5, "e")
+	tree.Put(6, "f")
+	tree.Put(7, "g")
+	tree.Put(3, "c")
+	tree.Put(4, "d")
+	tree.Put(1, "x")
+	tree.Put(2, "b")
+	tree.Put(1, "a") //overwrite
+
+	tree.Remove(5)
+	tree.Remove(6)
+	tree.Remove(7)
+	tree.Remove(8)
+	tree.Remove(5)
+
+	if actualValue, expectedValue := fmt.Sprintf("%d%d%d%d", tree.Keys()...), "1234"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if actualValue, expectedValue := fmt.Sprintf("%s%s%s%s", tree.Values()...), "abcd"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if actualValue, expectedValue := fmt.Sprintf("%s%s%s%s", tree.Values()...), "abcd"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if actualValue := tree.Size(); actualValue != 4 {
+		t.Errorf("Got %v expected %v", actualValue, 7)
+	}
+
+	tests2 := [][]interface{}{
+		{1, "a", true},
+		{2, "b", true},
+		{3, "c", true},
+		{4, "d", true},
+		{5, nil, false},
+		{6, nil, false},
+		{7, nil, false},
+		{8, nil, false},
+	}
+
+	for _, test := range tests2 {
+		actualValue, actualFound := tree.Get(test[0])
+		if actualValue != test[1] || actualFound != test[2] {
+			t.Errorf("Got %v expected %v", actualValue, test[1])
+		}
+	}
+
+	tree.Remove(1)
+	tree.Remove(4)
+	tree.Remove(2)
+	tree.Remove(3)
+	tree.Remove(2)
+	tree.Remove(2)
+
+	if actualValue, expectedValue := fmt.Sprintf("%s", tree.Keys()), "[]"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if actualValue, expectedValue := fmt.Sprintf("%s", tree.Values()), "[]"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if empty, size := tree.Empty(), tree.Size(); empty != true || size != -0 {
+		t.Errorf("Got %v expected %v", empty, true)
+	}
+
+}
+
+func TestAVLTreeLeftAndRight(t *testing.T) {
+	tree := NewWithIntComparator()
+
+	if actualValue := tree.Left(); actualValue != nil {
+		t.Errorf("Got %v expected %v", actualValue, nil)
+	}
+	if actualValue := tree.Right(); actualValue != nil {
+		t.Errorf("Got %v expected %v", actualValue, nil)
+	}
+
+	tree.Put(1, "a")
+	tree.Put(5, "e")
+	tree.Put(6, "f")
+	tree.Put(7, "g")
+	tree.Put(3, "c")
+	tree.Put(4, "d")
+	tree.Put(1, "x") // overwrite
+	tree.Put(2, "b")
+
+	if actualValue, expectedValue := fmt.Sprintf("%d", tree.Left().Key), "1"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if actualValue, expectedValue := fmt.Sprintf("%s", tree.Left().Value), "x"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+
+	if actualValue, expectedValue := fmt.Sprintf("%d", tree.Right().Key), "7"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if actualValue, expectedValue := fmt.Sprintf("%s", tree.Right().Value), "g"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+}
+
+func TestAVLTreeCeilingAndFloor(t *testing.T) {
+	tree := NewWithIntComparator()
+
+	if node, found := tree.Floor(0); node != nil || found {
+		t.Errorf("Got %v expected %v", node, "<nil>")
+	}
+	if node, found := tree.Ceiling(0); node != nil || found {
+		t.Errorf("Got %v expected %v", node, "<nil>")
+	}
+
+	tree.Put(5, "e")
+	tree.Put(6, "f")
+	tree.Put(7, "g")
+	tree.Put(3, "c")
+	tree.Put(4, "d")
+	tree.Put(1, "x")
+	tree.Put(2, "b")
+
+	if node, found := tree.Floor(4); node.Key != 4 || !found {
+		t.Errorf("Got %v expected %v", node.Key, 4)
+	}
+	if node, found := tree.Floor(0); node != nil || found {
+		t.Errorf("Got %v expected %v", node, "<nil>")
+	}
+
+	if node, found := tree.Ceiling(4); node.Key != 4 || !found {
+		t.Errorf("Got %v expected %v", node.Key, 4)
+	}
+	if node, found := tree.Ceiling(8); node != nil || found {
+		t.Errorf("Got %v expected %v", node, "<nil>")
+	}
+}
+
+func TestAVLTreeIteratorNextOnEmpty(t *testing.T) {
+	tree := NewWithIntComparator()
+	it := tree.Iterator()
+	for it.Next() {
+		t.Errorf("Shouldn't iterate on empty tree")
+	}
+}
+
+func TestAVLTreeIteratorPrevOnEmpty(t *testing.T) {
+	tree := NewWithIntComparator()
+	it := tree.Iterator()
+	for it.Prev() {
+		t.Errorf("Shouldn't iterate on empty tree")
+	}
+}
+
+func TestAVLTreeIterator1Next(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(5, "e")
+	tree.Put(6, "f")
+	tree.Put(7, "g")
+	tree.Put(3, "c")
+	tree.Put(4, "d")
+	tree.Put(1, "x")
+	tree.Put(2, "b")
+	tree.Put(1, "a") //overwrite
+	// │   ┌── 7
+	// └── 6
+	//     │   ┌── 5
+	//     └── 4
+	//         │   ┌── 3
+	//         └── 2
+	//             └── 1
+	it := tree.Iterator()
+	count := 0
+	for it.Next() {
+		count++
+		key := it.Key()
+		switch key {
+		case count:
+			if actualValue, expectedValue := key, count; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		default:
+			if actualValue, expectedValue := key, count; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		}
+	}
+	if actualValue, expectedValue := count, tree.Size(); actualValue != expectedValue {
+		t.Errorf("Size different. Got %v expected %v", actualValue, expectedValue)
+	}
+}
+
+func TestAVLTreeIterator1Prev(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(5, "e")
+	tree.Put(6, "f")
+	tree.Put(7, "g")
+	tree.Put(3, "c")
+	tree.Put(4, "d")
+	tree.Put(1, "x")
+	tree.Put(2, "b")
+	tree.Put(1, "a") //overwrite
+	// │   ┌── 7
+	// └── 6
+	//     │   ┌── 5
+	//     └── 4
+	//         │   ┌── 3
+	//         └── 2
+	//             └── 1
+	it := tree.Iterator()
+	for it.Next() {
+	}
+	countDown := tree.size
+	for it.Prev() {
+		key := it.Key()
+		switch key {
+		case countDown:
+			if actualValue, expectedValue := key, countDown; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		default:
+			if actualValue, expectedValue := key, countDown; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		}
+		countDown--
+	}
+	if actualValue, expectedValue := countDown, 0; actualValue != expectedValue {
+		t.Errorf("Size different. Got %v expected %v", actualValue, expectedValue)
+	}
+}
+
+func TestAVLTreeIterator2Next(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(3, "c")
+	tree.Put(1, "a")
+	tree.Put(2, "b")
+	it := tree.Iterator()
+	count := 0
+	for it.Next() {
+		count++
+		key := it.Key()
+		switch key {
+		case count:
+			if actualValue, expectedValue := key, count; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		default:
+			if actualValue, expectedValue := key, count; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		}
+	}
+	if actualValue, expectedValue := count, tree.Size(); actualValue != expectedValue {
+		t.Errorf("Size different. Got %v expected %v", actualValue, expectedValue)
+	}
+}
+
+func TestAVLTreeIterator2Prev(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(3, "c")
+	tree.Put(1, "a")
+	tree.Put(2, "b")
+	it := tree.Iterator()
+	for it.Next() {
+	}
+	countDown := tree.size
+	for it.Prev() {
+		key := it.Key()
+		switch key {
+		case countDown:
+			if actualValue, expectedValue := key, countDown; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		default:
+			if actualValue, expectedValue := key, countDown; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		}
+		countDown--
+	}
+	if actualValue, expectedValue := countDown, 0; actualValue != expectedValue {
+		t.Errorf("Size different. Got %v expected %v", actualValue, expectedValue)
+	}
+}
+
+func TestAVLTreeIterator3Next(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(1, "a")
+	it := tree.Iterator()
+	count := 0
+	for it.Next() {
+		count++
+		key := it.Key()
+		switch key {
+		case count:
+			if actualValue, expectedValue := key, count; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		default:
+			if actualValue, expectedValue := key, count; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		}
+	}
+	if actualValue, expectedValue := count, tree.Size(); actualValue != expectedValue {
+		t.Errorf("Size different. Got %v expected %v", actualValue, expectedValue)
+	}
+}
+
+func TestAVLTreeIterator3Prev(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(1, "a")
+	it := tree.Iterator()
+	for it.Next() {
+	}
+	countDown := tree.size
+	for it.Prev() {
+		key := it.Key()
+		switch key {
+		case countDown:
+			if actualValue, expectedValue := key, countDown; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		default:
+			if actualValue, expectedValue := key, countDown; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		}
+		countDown--
+	}
+	if actualValue, expectedValue := countDown, 0; actualValue != expectedValue {
+		t.Errorf("Size different. Got %v expected %v", actualValue, expectedValue)
+	}
+}
+
+func TestAVLTreeIterator4Next(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(13, 5)
+	tree.Put(8, 3)
+	tree.Put(17, 7)
+	tree.Put(1, 1)
+	tree.Put(11, 4)
+	tree.Put(15, 6)
+	tree.Put(25, 9)
+	tree.Put(6, 2)
+	tree.Put(22, 8)
+	tree.Put(27, 10)
+	// │           ┌── 27
+	// │       ┌── 25
+	// │       │   └── 22
+	// │   ┌── 17
+	// │   │   └── 15
+	// └── 13
+	//     │   ┌── 11
+	//     └── 8
+	//         │   ┌── 6
+	//         └── 1
+	it := tree.Iterator()
+	count := 0
+	for it.Next() {
+		count++
+		value := it.Value()
+		switch value {
+		case count:
+			if actualValue, expectedValue := value, count; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		default:
+			if actualValue, expectedValue := value, count; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		}
+	}
+	if actualValue, expectedValue := count, tree.Size(); actualValue != expectedValue {
+		t.Errorf("Size different. Got %v expected %v", actualValue, expectedValue)
+	}
+}
+
+func TestAVLTreeIterator4Prev(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(13, 5)
+	tree.Put(8, 3)
+	tree.Put(17, 7)
+	tree.Put(1, 1)
+	tree.Put(11, 4)
+	tree.Put(15, 6)
+	tree.Put(25, 9)
+	tree.Put(6, 2)
+	tree.Put(22, 8)
+	tree.Put(27, 10)
+	// │           ┌── 27
+	// │       ┌── 25
+	// │       │   └── 22
+	// │   ┌── 17
+	// │   │   └── 15
+	// └── 13
+	//     │   ┌── 11
+	//     └── 8
+	//         │   ┌── 6
+	//         └── 1
+	it := tree.Iterator()
+	count := tree.Size()
+	for it.Next() {
+	}
+	for it.Prev() {
+		value := it.Value()
+		switch value {
+		case count:
+			if actualValue, expectedValue := value, count; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		default:
+			if actualValue, expectedValue := value, count; actualValue != expectedValue {
+				t.Errorf("Got %v expected %v", actualValue, expectedValue)
+			}
+		}
+		count--
+	}
+	if actualValue, expectedValue := count, 0; actualValue != expectedValue {
+		t.Errorf("Size different. Got %v expected %v", actualValue, expectedValue)
+	}
+}
+
+func TestAVLTreeIteratorBegin(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(3, "c")
+	tree.Put(1, "a")
+	tree.Put(2, "b")
+	it := tree.Iterator()
+
+	it.Begin()
+
+	i := 0
+	for it.Next() {
+		i++
+	}
+	if i != 3 {
+		t.Errorf("Got %d expected %d\n", i, tree.Size())
+	}
+
+	it.Begin()
+	it.Next()
+	if key, value := it.Key(), it.Value(); key != 1 || value != "a" {
+		t.Errorf("Got %v,%v expected %v,%v", key, value, 1, "a")
+	}
+}
+
+func TestAVLTreeIteratorEnd(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(3, "c")
+	tree.Put(1, "a")
+	tree.Put(2, "b")
+	it := tree.Iterator()
+
+	it.End()
+
+	i := 0
+	for it.Prev() {
+		i++
+	}
+	if i != 3 {
+		t.Errorf("Got %d expected %d\n", i, tree.Size())
+	}
+
+	it.End()
+	it.Prev()
+	if key, value := it.Key(), it.Value(); key != 3 || value != "c" {
+		t.Errorf("Got %v,%v expected %v,%v", key, value, 3, "c")
+	}
+}
+
+func TestAVLTreeIteratorFirst(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(3, "c")
+	tree.Put(1, "a")
+	tree.Put(2, "b")
+	it := tree.Iterator()
+	if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if key, value := it.Key(), it.Value(); key != 1 || value != "a" {
+		t.Errorf("Got %v,%v expected %v,%v", key, value, 1, "a")
+	}
+}
+
+func TestAVLTreeIteratorLast(t *testing.T) {
+	tree := NewWithIntComparator()
+	tree.Put(3, "c")
+	tree.Put(1, "a")
+	tree.Put(2, "b")
+	it := tree.Iterator()
+	if actualValue, expectedValue := it.Last(), true; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+	if key, value := it.Key(), it.Value(); key != 3 || value != "c" {
+		t.Errorf("Got %v,%v expected %v,%v", key, value, 3, "c")
+	}
+}
+
+func benchmarkGet(b *testing.B, tree *Tree, size int) {
+	for i := 0; i < b.N; i++ {
+		for n := 0; n < size; n++ {
+			tree.Get(n)
+		}
+	}
+}
+
+func benchmarkPut(b *testing.B, tree *Tree, size int) {
+	for i := 0; i < b.N; i++ {
+		for n := 0; n < size; n++ {
+			tree.Put(n, struct{}{})
+		}
+	}
+}
+
+func benchmarkRemove(b *testing.B, tree *Tree, size int) {
+	for i := 0; i < b.N; i++ {
+		for n := 0; n < size; n++ {
+			tree.Remove(n)
+		}
+	}
+}
+
+func BenchmarkAVLTreeGet100(b *testing.B) {
+	b.StopTimer()
+	size := 100
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkGet(b, tree, size)
+}
+
+func BenchmarkAVLTreeGet1000(b *testing.B) {
+	b.StopTimer()
+	size := 1000
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkGet(b, tree, size)
+}
+
+func BenchmarkAVLTreeGet10000(b *testing.B) {
+	b.StopTimer()
+	size := 10000
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkGet(b, tree, size)
+}
+
+func BenchmarkAVLTreeGet100000(b *testing.B) {
+	b.StopTimer()
+	size := 100000
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkGet(b, tree, size)
+}
+
+func BenchmarkAVLTreePut100(b *testing.B) {
+	b.StopTimer()
+	size := 100
+	tree := NewWithIntComparator()
+	b.StartTimer()
+	benchmarkPut(b, tree, size)
+}
+
+func BenchmarkAVLTreePut1000(b *testing.B) {
+	b.StopTimer()
+	size := 1000
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkPut(b, tree, size)
+}
+
+func BenchmarkAVLTreePut10000(b *testing.B) {
+	b.StopTimer()
+	size := 10000
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkPut(b, tree, size)
+}
+
+func BenchmarkAVLTreePut100000(b *testing.B) {
+	b.StopTimer()
+	size := 100000
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkPut(b, tree, size)
+}
+
+func BenchmarkAVLTreeRemove100(b *testing.B) {
+	b.StopTimer()
+	size := 100
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkRemove(b, tree, size)
+}
+
+func BenchmarkAVLTreeRemove1000(b *testing.B) {
+	b.StopTimer()
+	size := 1000
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkRemove(b, tree, size)
+}
+
+func BenchmarkAVLTreeRemove10000(b *testing.B) {
+	b.StopTimer()
+	size := 10000
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkRemove(b, tree, size)
+}
+
+func BenchmarkAVLTreeRemove100000(b *testing.B) {
+	b.StopTimer()
+	size := 100000
+	tree := NewWithIntComparator()
+	for n := 0; n < size; n++ {
+		tree.Put(n, struct{}{})
+	}
+	b.StartTimer()
+	benchmarkRemove(b, tree, size)
+}
diff --git a/trees/avltree/iterator.go b/trees/avltree/iterator.go
new file mode 100644
index 0000000..b61bc82
--- /dev/null
+++ b/trees/avltree/iterator.go
@@ -0,0 +1,111 @@
+// Copyright (c) 2017, Benjamin Scher Purcell. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package avltree
+
+import "github.com/emirpasic/gods/containers"
+
+func assertIteratorImplementation() {
+	var _ containers.ReverseIteratorWithKey = (*Iterator)(nil)
+}
+
+// Iterator holding the iterator's state
+type Iterator struct {
+	tree     *Tree
+	node     *Node
+	position position
+}
+
+type position byte
+
+const (
+	begin, between, end position = 0, 1, 2
+)
+
+// Iterator returns a stateful iterator whose elements are key/value pairs.
+func (tree *Tree) Iterator() containers.ReverseIteratorWithKey {
+	return &Iterator{tree: tree, node: nil, position: begin}
+}
+
+// Next moves the iterator to the next element and returns true if there was a next element in the container.
+// If Next() returns true, then next element's key and value can be retrieved by Key() and Value().
+// If Next() was called for the first time, then it will point the iterator to the first element if it exists.
+// Modifies the state of the iterator.
+func (iter *Iterator) Next() bool {
+	switch iter.position {
+	case begin:
+		iter.position = between
+		iter.node = iter.tree.Left()
+	case between:
+		iter.node = iter.node.Next()
+	}
+
+	if iter.node == nil {
+		iter.position = end
+		return false
+	}
+	return true
+}
+
+// Prev moves the iterator to the next element and returns true if there was a previous element in the container.
+// If Prev() returns true, then next element's key and value can be retrieved by Key() and Value().
+// If Prev() was called for the first time, then it will point the iterator to the first element if it exists.
+// Modifies the state of the iterator.
+func (iter *Iterator) Prev() bool {
+	switch iter.position {
+	case end:
+		iter.position = between
+		iter.node = iter.tree.Right()
+	case between:
+		iter.node = iter.node.Prev()
+	}
+
+	if iter.node == nil {
+		iter.position = begin
+		return false
+	}
+	return true
+}
+
+// Value returns the current element's value.
+// Does not modify the state of the iterator.
+func (iter *Iterator) Value() interface{} {
+	return iter.node.Value
+}
+
+// Key returns the current element's key.
+// Does not modify the state of the iterator.
+func (iter *Iterator) Key() interface{} {
+	return iter.node.Key
+}
+
+// Begin resets the iterator to its initial state (one-before-first)
+// Call Next() to fetch the first element if any.
+func (iter *Iterator) Begin() {
+	iter.node = nil
+	iter.position = begin
+}
+
+// End moves the iterator past the last element (one-past-the-end).
+// Call Prev() to fetch the last element if any.
+func (iter *Iterator) End() {
+	iter.node = nil
+	iter.position = end
+}
+
+// First moves the iterator to the first element and returns true if there was a first element in the container.
+// If First() returns true, then first element's key and value can be retrieved by Key() and Value().
+// Modifies the state of the iterator
+func (iter *Iterator) First() bool {
+	iter.Begin()
+	return iter.Next()
+}
+
+// Last moves the iterator to the last element and returns true if there was a last element in the container.
+// If Last() returns true, then last element's key and value can be retrieved by Key() and Value().
+// Modifies the state of the iterator.
+func (iter *Iterator) Last() bool {
+	iter.End()
+	return iter.Prev()
+}
diff --git a/trees/binaryheap/binaryheap.go b/trees/binaryheap/binaryheap.go
index 70b28cf..e69d4d5 100644
--- a/trees/binaryheap/binaryheap.go
+++ b/trees/binaryheap/binaryheap.go
@@ -13,14 +13,15 @@ package binaryheap
 
 import (
 	"fmt"
+	"strings"
+
+	"github.com/emirpasic/gods/containers"
 	"github.com/emirpasic/gods/lists/arraylist"
-	"github.com/emirpasic/gods/trees"
 	"github.com/emirpasic/gods/utils"
-	"strings"
 )
 
 func assertTreeImplementation() {
-	var _ trees.Tree = (*Heap)(nil)
+	var _ containers.Container = (*Heap)(nil)
 }
 
 // Heap holds elements in an array-list
diff --git a/trees/btree/btree.go b/trees/btree/btree.go
index 5f86699..9ba6f5b 100644
--- a/trees/btree/btree.go
+++ b/trees/btree/btree.go
@@ -19,7 +19,7 @@ package btree
 import (
 	"bytes"
 	"fmt"
-	"github.com/emirpasic/gods/trees"
+	"github.com/spewspews/gods/trees"
 	"github.com/emirpasic/gods/utils"
 	"strings"
 )
@@ -31,7 +31,7 @@ func assertTreeImplementation() {
 // Tree holds elements of the B-tree
 type Tree struct {
 	Root       *Node            // Root node
-	Comparator utils.Comparator // Key comparator
+	comparator utils.Comparator // Key comparator
 	size       int              // Total number of keys in the tree
 	m          int              // order (maximum number of children)
 }
@@ -54,7 +54,7 @@ func NewWith(order int, comparator utils.Comparator) *Tree {
 	if order < 3 {
 		panic("Invalid order, should be at least 3")
 	}
-	return &Tree{m: order, Comparator: comparator}
+	return &Tree{m: order, comparator: comparator}
 }
 
 // NewWithIntComparator instantiates a B-tree with the order (maximum number of children) and the IntComparator, i.e. keys are of type int.
@@ -105,6 +105,11 @@ func (tree *Tree) Remove(key interface{}) {
 	}
 }
 
+// New returns an empty tree with the same comparator
+func (tree *Tree) New() trees.Tree {
+	return &Tree{m: tree.m, comparator: tree.comparator}
+}
+
 // Empty returns true if tree does not contain any nodes
 func (tree *Tree) Empty() bool {
 	return tree.size == 0
@@ -167,6 +172,15 @@ func (tree *Tree) LeftValue() interface{} {
 	return nil
 }
 
+// Min returns the minimum key value pair in the tree.
+func (tree *Tree) Min() (interface{}, interface{}) {
+	n := tree.Left()
+	if n == nil {
+		return nil, nil
+	}
+	return n.Entries[0].Key, n.Entries[0].Value
+}
+
 // Right returns the right-most (max) node or nil if tree is empty.
 func (tree *Tree) Right() *Node {
 	return tree.right(tree.Root)
@@ -188,6 +202,16 @@ func (tree *Tree) RightValue() interface{} {
 	return nil
 }
 
+// Max returns the minimum key value pair in the tree.
+func (tree *Tree) Max() (interface{}, interface{}) {
+	n := tree.Right()
+	if n == nil {
+		return nil, nil
+	}
+	l := len(n.Entries)-1
+	return n.Entries[l].Key, n.Entries[l].Value
+}
+
 // String returns a string representation of container (for debugging purposes)
 func (tree *Tree) String() string {
 	var buffer bytes.Buffer
@@ -266,7 +290,7 @@ func (tree *Tree) search(node *Node, key interface{}) (index int, found bool) {
 	var mid int
 	for low <= high {
 		mid = (high + low) / 2
-		compare := tree.Comparator(key, node.Entries[mid].Key)
+		compare := tree.comparator(key, node.Entries[mid].Key)
 		switch {
 		case compare > 0:
 			low = mid + 1
diff --git a/trees/btree/btree_test.go b/trees/btree/btree_test.go
index 4705bc1..67890e6 100644
--- a/trees/btree/btree_test.go
+++ b/trees/btree/btree_test.go
@@ -929,25 +929,17 @@ func TestBTreeIteratorBegin(t *testing.T) {
 	tree.Put(2, "b")
 	it := tree.Iterator()
 
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
-	}
-
 	it.Begin()
 
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
-	}
-
+	i := 0
 	for it.Next() {
+		i++
 	}
-
-	it.Begin()
-
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
+	if i != 3 {
+		t.Errorf("Got %d expected %d\n", i, tree.Size())
 	}
 
+	it.Begin()
 	it.Next()
 	if key, value := it.Key(), it.Value(); key != 1 || value != "a" {
 		t.Errorf("Got %v,%v expected %v,%v", key, value, 1, "a")
@@ -956,25 +948,22 @@ func TestBTreeIteratorBegin(t *testing.T) {
 
 func TestBTreeIteratorEnd(t *testing.T) {
 	tree := NewWithIntComparator(3)
-	it := tree.Iterator()
-
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
-	}
-
-	it.End()
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
-	}
-
 	tree.Put(3, "c")
 	tree.Put(1, "a")
 	tree.Put(2, "b")
+	it := tree.Iterator()
+
 	it.End()
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
+
+	i := 0
+	for it.Prev() {
+		i++
+	}
+	if i != 3 {
+		t.Errorf("Got %d expected %d\n", i, tree.Size())
 	}
 
+	it.End()
 	it.Prev()
 	if key, value := it.Key(), it.Value(); key != 3 || value != "c" {
 		t.Errorf("Got %v,%v expected %v,%v", key, value, 3, "c")
diff --git a/trees/btree/iterator.go b/trees/btree/iterator.go
index 840db68..c01c519 100644
--- a/trees/btree/iterator.go
+++ b/trees/btree/iterator.go
@@ -25,8 +25,8 @@ const (
 )
 
 // Iterator returns a stateful iterator whose elements are key/value pairs.
-func (tree *Tree) Iterator() Iterator {
-	return Iterator{tree: tree, node: nil, position: begin}
+func (tree *Tree) Iterator() containers.ReverseIteratorWithKey {
+	return &Iterator{tree: tree, node: nil, position: begin}
 }
 
 // Next moves the iterator to the next element and returns true if there was a next element in the container.
diff --git a/trees/redblacktree/iterator.go b/trees/redblacktree/iterator.go
index 90b84af..56bf5a5 100644
--- a/trees/redblacktree/iterator.go
+++ b/trees/redblacktree/iterator.go
@@ -24,8 +24,8 @@ const (
 )
 
 // Iterator returns a stateful iterator whose elements are key/value pairs.
-func (tree *Tree) Iterator() Iterator {
-	return Iterator{tree: tree, node: nil, position: begin}
+func (tree *Tree) Iterator() containers.ReverseIteratorWithKey {
+	return &Iterator{tree: tree, node: nil, position: begin}
 }
 
 // Next moves the iterator to the next element and returns true if there was a next element in the container.
@@ -55,7 +55,7 @@ func (iterator *Iterator) Next() bool {
 		node := iterator.node
 		for iterator.node.Parent != nil {
 			iterator.node = iterator.node.Parent
-			if iterator.tree.Comparator(node.Key, iterator.node.Key) <= 0 {
+			if iterator.tree.comparator(node.Key, iterator.node.Key) <= 0 {
 				goto between
 			}
 		}
@@ -97,7 +97,7 @@ func (iterator *Iterator) Prev() bool {
 		node := iterator.node
 		for iterator.node.Parent != nil {
 			iterator.node = iterator.node.Parent
-			if iterator.tree.Comparator(node.Key, iterator.node.Key) >= 0 {
+			if iterator.tree.comparator(node.Key, iterator.node.Key) >= 0 {
 				goto between
 			}
 		}
diff --git a/trees/redblacktree/redblacktree.go b/trees/redblacktree/redblacktree.go
index f9c9bc9..aba9866 100644
--- a/trees/redblacktree/redblacktree.go
+++ b/trees/redblacktree/redblacktree.go
@@ -13,8 +13,9 @@ package redblacktree
 
 import (
 	"fmt"
-	"github.com/emirpasic/gods/trees"
+
 	"github.com/emirpasic/gods/utils"
+	"github.com/spewspews/gods/trees"
 )
 
 func assertTreeImplementation() {
@@ -31,7 +32,7 @@ const (
 type Tree struct {
 	Root       *Node
 	size       int
-	Comparator utils.Comparator
+	comparator utils.Comparator
 }
 
 // Node is a single element within the tree
@@ -46,17 +47,27 @@ type Node struct {
 
 // NewWith instantiates a red-black tree with the custom comparator.
 func NewWith(comparator utils.Comparator) *Tree {
-	return &Tree{Comparator: comparator}
+	return &Tree{comparator: comparator}
 }
 
 // NewWithIntComparator instantiates a red-black tree with the IntComparator, i.e. keys are of type int.
 func NewWithIntComparator() *Tree {
-	return &Tree{Comparator: utils.IntComparator}
+	return &Tree{comparator: utils.IntComparator}
 }
 
 // NewWithStringComparator instantiates a red-black tree with the StringComparator, i.e. keys are of type string.
 func NewWithStringComparator() *Tree {
-	return &Tree{Comparator: utils.StringComparator}
+	return &Tree{comparator: utils.StringComparator}
+}
+
+// Comparator returns the comparator function for the tree.
+func (tree *Tree) Comparator() utils.Comparator {
+	return tree.comparator
+}
+
+// New returns a new empty tree with the same comparator.
+func (tree *Tree) New() trees.Tree {
+	return &Tree{comparator: tree.comparator}
 }
 
 // Put inserts node into the tree.
@@ -69,7 +80,7 @@ func (tree *Tree) Put(key interface{}, value interface{}) {
 		node := tree.Root
 		loop := true
 		for loop {
-			compare := tree.Comparator(key, node.Key)
+			compare := tree.comparator(key, node.Key)
 			switch {
 			case compare == 0:
 				node.Key = key
@@ -192,6 +203,26 @@ func (tree *Tree) Right() *Node {
 	return parent
 }
 
+// Min returns the minimum key value pair of the AVL tree
+// or nils if the tree is empty.
+func (tree *Tree) Min() (interface{}, interface{}) {
+	n := tree.Left()
+	if n == nil {
+		return nil, nil
+	}
+	return n.Key, n.Value
+}
+
+// Max returns the minimum key value pair of the AVL tree
+// or nils if the tree is empty.
+func (tree *Tree) Max() (interface{}, interface{}) {
+	n := tree.Right()
+	if n == nil {
+		return nil, nil
+	}
+	return n.Key, n.Value
+}
+
 // Floor Finds floor node of the input key, return the floor node or nil if no ceiling is found.
 // Second return parameter is true if floor was found, otherwise false.
 //
@@ -204,7 +235,7 @@ func (tree *Tree) Floor(key interface{}) (floor *Node, found bool) {
 	found = false
 	node := tree.Root
 	for node != nil {
-		compare := tree.Comparator(key, node.Key)
+		compare := tree.comparator(key, node.Key)
 		switch {
 		case compare == 0:
 			return node, true
@@ -233,7 +264,7 @@ func (tree *Tree) Ceiling(key interface{}) (ceiling *Node, found bool) {
 	found = false
 	node := tree.Root
 	for node != nil {
-		compare := tree.Comparator(key, node.Key)
+		compare := tree.comparator(key, node.Key)
 		switch {
 		case compare == 0:
 			return node, true
@@ -300,7 +331,7 @@ func output(node *Node, prefix string, isTail bool, str *string) {
 func (tree *Tree) lookup(key interface{}) *Node {
 	node := tree.Root
 	for node != nil {
-		compare := tree.Comparator(key, node.Key)
+		compare := tree.comparator(key, node.Key)
 		switch {
 		case compare == 0:
 			return node
diff --git a/trees/redblacktree/redblacktree_test.go b/trees/redblacktree/redblacktree_test.go
index 714defc..f2e10b7 100644
--- a/trees/redblacktree/redblacktree_test.go
+++ b/trees/redblacktree/redblacktree_test.go
@@ -477,25 +477,17 @@ func TestRedBlackTreeIteratorBegin(t *testing.T) {
 	tree.Put(2, "b")
 	it := tree.Iterator()
 
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
-	}
-
 	it.Begin()
 
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
-	}
-
+	i := 0
 	for it.Next() {
+		i++
 	}
-
-	it.Begin()
-
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
+	if i != 3 {
+		t.Errorf("Got %d expected %d\n", i, tree.Size())
 	}
 
+	it.Begin()
 	it.Next()
 	if key, value := it.Key(), it.Value(); key != 1 || value != "a" {
 		t.Errorf("Got %v,%v expected %v,%v", key, value, 1, "a")
@@ -504,25 +496,22 @@ func TestRedBlackTreeIteratorBegin(t *testing.T) {
 
 func TestRedBlackTreeIteratorEnd(t *testing.T) {
 	tree := NewWithIntComparator()
-	it := tree.Iterator()
-
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
-	}
-
-	it.End()
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
-	}
-
 	tree.Put(3, "c")
 	tree.Put(1, "a")
 	tree.Put(2, "b")
+	it := tree.Iterator()
+
 	it.End()
-	if it.node != nil {
-		t.Errorf("Got %v expected %v", it.node, nil)
+
+	i := 0
+	for it.Prev() {
+		i++
+	}
+	if i != 3 {
+		t.Errorf("Got %d expected %d\n", i, tree.Size())
 	}
 
+	it.End()
 	it.Prev()
 	if key, value := it.Key(), it.Value(); key != 3 || value != "c" {
 		t.Errorf("Got %v,%v expected %v,%v", key, value, 3, "c")
diff --git a/trees/trees.go b/trees/trees.go
index a5a7427..4a13b83 100644
--- a/trees/trees.go
+++ b/trees/trees.go
@@ -13,6 +13,15 @@ import "github.com/emirpasic/gods/containers"
 
 // Tree interface that all trees implement
 type Tree interface {
+	New() Tree
+	Iterator() containers.ReverseIteratorWithKey
+	Put(key interface{}, value interface{})
+	Remove(key interface{})
+	Get(key interface{}) (interface{}, bool)
+	Keys() []interface{}
+	Min() (interface{}, interface{})
+	Max() (interface{}, interface{})
+
 	containers.Container
 	// Empty() bool
 	// Size() int