From 6bfa9f318d6341686712b65c50b76b239fa93de0 Mon Sep 17 00:00:00 2001
From: Vlad Alexandru Ionescu <vlad.alexandru.ionescu@gmail.com>
Date: Tue, 19 Apr 2016 21:38:32 +0100
Subject: [PATCH] Add ability to get leftmost (minimum) and rightmost (maximum)
 keys in treemap.

---
 maps/treemap/treemap.go            | 10 ++++++++
 maps/treemap/treemap_test.go       | 34 ++++++++++++++++----------
 trees/redblacktree/redblacktree.go | 38 ++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 12 deletions(-)

diff --git a/maps/treemap/treemap.go b/maps/treemap/treemap.go
index 6386d69..06d6185 100644
--- a/maps/treemap/treemap.go
+++ b/maps/treemap/treemap.go
@@ -73,6 +73,16 @@ func (m *Map) Get(key interface{}) (value interface{}, found bool) {
 	return m.tree.Get(key)
 }
 
+// Returns the left-most element in the tree map (minimum).
+func (m *Map) Left() (key interface{}) {
+	return m.tree.Left()
+}
+
+// Returns the right-most element in the tree map (maximum).
+func (m *Map) Right() (key interface{}) {
+	return m.tree.Right()
+}
+
 // Remove the element from the map by key.
 // Key should adhere to the comparator's type assertion, otherwise method panics.
 func (m *Map) Remove(key interface{}) {
diff --git a/maps/treemap/treemap_test.go b/maps/treemap/treemap_test.go
index 03fb23c..9bdfd63 100644
--- a/maps/treemap/treemap_test.go
+++ b/maps/treemap/treemap_test.go
@@ -51,13 +51,23 @@ func TestTreeMap(t *testing.T) {
 	}
 
 	// test Keys()
-	if actualValue, expactedValue := fmt.Sprintf("%d%d%d%d%d%d%d", m.Keys()...), "1234567"; actualValue != expactedValue {
-		t.Errorf("Got %v expected %v", actualValue, expactedValue)
+	if actualValue, expectedValue := fmt.Sprintf("%d%d%d%d%d%d%d", m.Keys()...), "1234567"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
 	}
 
 	// test Values()
-	if actualValue, expactedValue := fmt.Sprintf("%s%s%s%s%s%s%s", m.Values()...), "abcdefg"; actualValue != expactedValue {
-		t.Errorf("Got %v expected %v", actualValue, expactedValue)
+	if actualValue, expectedValue := fmt.Sprintf("%s%s%s%s%s%s%s", m.Values()...), "abcdefg"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+
+	// test Left()
+	if actualValue, expectedValue := fmt.Sprintf("%d", m.Left()), "1"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
+	}
+
+	// test Right()
+	if actualValue, expectedValue := fmt.Sprintf("%d", m.Right()), "7"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
 	}
 
 	// key,expectedValue,expectedFound
@@ -88,13 +98,13 @@ func TestTreeMap(t *testing.T) {
 	m.Remove(5)
 
 	// Test Keys()
-	if actualValue, expactedValue := fmt.Sprintf("%d%d%d%d", m.Keys()...), "1234"; actualValue != expactedValue {
-		t.Errorf("Got %v expected %v", actualValue, expactedValue)
+	if actualValue, expectedValue := fmt.Sprintf("%d%d%d%d", m.Keys()...), "1234"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
 	}
 
 	// test Values()
-	if actualValue, expactedValue := fmt.Sprintf("%s%s%s%s", m.Values()...), "abcd"; actualValue != expactedValue {
-		t.Errorf("Got %v expected %v", actualValue, expactedValue)
+	if actualValue, expectedValue := fmt.Sprintf("%s%s%s%s", m.Values()...), "abcd"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
 	}
 
 	// Test Size()
@@ -130,13 +140,13 @@ func TestTreeMap(t *testing.T) {
 	m.Remove(2)
 
 	// Test Keys()
-	if actualValue, expactedValue := fmt.Sprintf("%s", m.Keys()), "[]"; actualValue != expactedValue {
-		t.Errorf("Got %v expected %v", actualValue, expactedValue)
+	if actualValue, expectedValue := fmt.Sprintf("%s", m.Keys()), "[]"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
 	}
 
 	// test Values()
-	if actualValue, expactedValue := fmt.Sprintf("%s", m.Values()), "[]"; actualValue != expactedValue {
-		t.Errorf("Got %v expected %v", actualValue, expactedValue)
+	if actualValue, expectedValue := fmt.Sprintf("%s", m.Values()), "[]"; actualValue != expectedValue {
+		t.Errorf("Got %v expected %v", actualValue, expectedValue)
 	}
 
 	// Test Size()
diff --git a/trees/redblacktree/redblacktree.go b/trees/redblacktree/redblacktree.go
index 507b8d1..67f83b2 100644
--- a/trees/redblacktree/redblacktree.go
+++ b/trees/redblacktree/redblacktree.go
@@ -186,6 +186,24 @@ func (tree *Tree) Values() []interface{} {
 	return values
 }
 
+// Returns the left-most key.
+func (tree *Tree) Left() interface{} {
+	left := tree.leftNode()
+	if left == nil {
+		return nil
+	}
+	return left.Key
+}
+
+// Returns the right-most key.
+func (tree *Tree) Right() interface{} {
+	right := tree.rightNode()
+	if right == nil {
+		return nil
+	}
+	return right.Key
+}
+
 // Removes all nodes from the tree.
 func (tree *Tree) Clear() {
 	tree.Root = nil
@@ -232,6 +250,26 @@ func (tree *Tree) inOrder() []*Node {
 	return nodes
 }
 
+func (tree *Tree) leftNode() *Node {
+	var parent *Node
+	current := tree.Root
+	for current != nil {
+		parent = current
+		current = current.Left
+	}
+	return parent
+}
+
+func (tree *Tree) rightNode() *Node {
+	var parent *Node
+	current := tree.Root
+	for current != nil {
+		parent = current
+		current = current.Right
+	}
+	return parent
+}
+
 func output(node *Node, prefix string, isTail bool, str *string) {
 	if node.Right != nil {
 		newPrefix := prefix