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Fix iterator in binary heap

Browse Source
pull/203/head
Emir Pasic 2 years ago
parent 33e824351c
commit 6b0ffefe7f
3 changed files with 74 additions and 38 deletions
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10
trees/binaryheap/binaryheap.go
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@ -97,15 +97,19 @@ func (heap *Heap) Clear() {
// Values returns all elements in the heap.
func (heap *Heap) Values() []interface{} {
return heap.list.Values()
values := make([]interface{}, heap.list.Size(), heap.list.Size())
for it := heap.Iterator(); it.Next(); {
values[it.Index()] = it.Value()
}
return values
}
// String returns a string representation of container
func (heap *Heap) String() string {
str := "BinaryHeap\n"
values := []string{}
for _, value := range heap.list.Values() {
values = append(values, fmt.Sprintf("%v", value))
for it := heap.Iterator(); it.Next(); {
values = append(values, fmt.Sprintf("%v", it.Value()))
}
str += strings.Join(values, ", ")
return str

66
trees/binaryheap/binaryheap_test.go
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@ -18,11 +18,11 @@ func TestBinaryHeapPush(t *testing.T) {
t.Errorf("Got %v expected %v", actualValue, true)
}
heap.Push(3) // [3]
heap.Push(2) // [2,3]
heap.Push(1) // [1,3,2](2 swapped with 1, hence last)
heap.Push(3)
heap.Push(2)
heap.Push(1)
if actualValue := heap.Values(); actualValue[0].(int) != 1 || actualValue[1].(int) != 3 || actualValue[2].(int) != 2 {
if actualValue := heap.Values(); actualValue[0].(int) != 1 || actualValue[1].(int) != 2 || actualValue[2].(int) != 3 {
t.Errorf("Got %v expected %v", actualValue, "[1,2,3]")
}
if actualValue := heap.Empty(); actualValue != false {
@ -56,10 +56,10 @@ func TestBinaryHeapPop(t *testing.T) {
t.Errorf("Got %v expected %v", actualValue, true)
}
heap.Push(3) // [3]
heap.Push(2) // [2,3]
heap.Push(1) // [1,3,2](2 swapped with 1, hence last)
heap.Pop() // [3,2]
heap.Push(3)
heap.Push(2)
heap.Push(1)
heap.Pop()
if actualValue, ok := heap.Peek(); actualValue != 2 || !ok {
t.Errorf("Got %v expected %v", actualValue, 2)
@ -110,9 +110,9 @@ func TestBinaryHeapIteratorOnEmpty(t *testing.T) {
func TestBinaryHeapIteratorNext(t *testing.T) {
heap := NewWithIntComparator()
heap.Push(3) // [3]
heap.Push(2) // [2,3]
heap.Push(1) // [1,3,2](2 swapped with 1, hence last)
heap.Push(3)
heap.Push(2)
heap.Push(1)
it := heap.Iterator()
count := 0
@ -126,11 +126,11 @@ func TestBinaryHeapIteratorNext(t *testing.T) {
t.Errorf("Got %v expected %v", actualValue, expectedValue)
}
case 1:
if actualValue, expectedValue := value, 3; actualValue != expectedValue {
if actualValue, expectedValue := value, 2; actualValue != expectedValue {
t.Errorf("Got %v expected %v", actualValue, expectedValue)
}
case 2:
if actualValue, expectedValue := value, 2; actualValue != expectedValue {
if actualValue, expectedValue := value, 3; actualValue != expectedValue {
t.Errorf("Got %v expected %v", actualValue, expectedValue)
}
default:
@ -147,9 +147,9 @@ func TestBinaryHeapIteratorNext(t *testing.T) {
func TestBinaryHeapIteratorPrev(t *testing.T) {
heap := NewWithIntComparator()
heap.Push(3) // [3]
heap.Push(2) // [2,3]
heap.Push(1) // [1,3,2](2 swapped with 1, hence last)
heap.Push(3)
heap.Push(2)
heap.Push(1)
it := heap.Iterator()
for it.Next() {
@ -165,11 +165,11 @@ func TestBinaryHeapIteratorPrev(t *testing.T) {
t.Errorf("Got %v expected %v", actualValue, expectedValue)
}
case 1:
if actualValue, expectedValue := value, 3; actualValue != expectedValue {
if actualValue, expectedValue := value, 2; actualValue != expectedValue {
t.Errorf("Got %v expected %v", actualValue, expectedValue)
}
case 2:
if actualValue, expectedValue := value, 2; actualValue != expectedValue {
if actualValue, expectedValue := value, 3; actualValue != expectedValue {
t.Errorf("Got %v expected %v", actualValue, expectedValue)
}
default:
@ -213,17 +213,17 @@ func TestBinaryHeapIteratorEnd(t *testing.T) {
t.Errorf("Got %v expected %v", index, 0)
}
heap.Push(3) // [3]
heap.Push(2) // [2,3]
heap.Push(1) // [1,3,2](2 swapped with 1, hence last)
heap.Push(3)
heap.Push(2)
heap.Push(1)
it.End()
if index := it.Index(); index != heap.Size() {
t.Errorf("Got %v expected %v", index, heap.Size())
}
it.Prev()
if index, value := it.Index(), it.Value(); index != heap.Size()-1 || value != 2 {
t.Errorf("Got %v,%v expected %v,%v", index, value, heap.Size()-1, 2)
if index, value := it.Index(), it.Value(); index != heap.Size()-1 || value != 3 {
t.Errorf("Got %v,%v expected %v,%v", index, value, heap.Size()-1, 3)
}
}
@ -233,9 +233,9 @@ func TestBinaryHeapIteratorFirst(t *testing.T) {
if actualValue, expectedValue := it.First(), false; actualValue != expectedValue {
t.Errorf("Got %v expected %v", actualValue, expectedValue)
}
heap.Push(3) // [3]
heap.Push(2) // [2,3]
heap.Push(1) // [1,3,2](2 swapped with 1, hence last)
heap.Push(3)
heap.Push(2)
heap.Push(1)
if actualValue, expectedValue := it.First(), true; actualValue != expectedValue {
t.Errorf("Got %v expected %v", actualValue, expectedValue)
}
@ -252,12 +252,12 @@ func TestBinaryHeapIteratorLast(t *testing.T) {
}
tree.Push(2)
tree.Push(3)
tree.Push(1) // [1,3,2](2 swapped with 1, hence last)
tree.Push(1)
if actualValue, expectedValue := it.Last(), true; actualValue != expectedValue {
t.Errorf("Got %v expected %v", actualValue, expectedValue)
}
if index, value := it.Index(), it.Value(); index != 2 || value != 2 {
t.Errorf("Got %v,%v expected %v,%v", index, value, 2, 2)
if index, value := it.Index(), it.Value(); index != 2 || value != 3 {
t.Errorf("Got %v,%v expected %v,%v", index, value, 2, 3)
}
}
@ -370,13 +370,13 @@ func TestBinaryHeapIteratorPrevTo(t *testing.T) {
func TestBinaryHeapSerialization(t *testing.T) {
heap := NewWithStringComparator()
heap.Push("c") // ["c"]
heap.Push("b") // ["b","c"]
heap.Push("a") // ["a","c","b"]("b" swapped with "a", hence last)
heap.Push("c")
heap.Push("b")
heap.Push("a")
var err error
assert := func() {
if actualValue := heap.Values(); actualValue[0].(string) != "a" || actualValue[1].(string) != "c" || actualValue[2].(string) != "b" {
if actualValue := heap.Values(); actualValue[0].(string) != "a" || actualValue[1].(string) != "b" || actualValue[2].(string) != "c" {
t.Errorf("Got %v expected %v", actualValue, "[1,3,2]")
}
if actualValue := heap.Size(); actualValue != 3 {

36
trees/binaryheap/iterator.go
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@ -4,7 +4,9 @@
package binaryheap
import "github.com/emirpasic/gods/containers"
import (
"github.com/emirpasic/gods/containers"
)
// Assert Iterator implementation
var _ containers.ReverseIteratorWithIndex = (*Iterator)(nil)
@ -44,7 +46,19 @@ func (iterator *Iterator) Prev() bool {
// Value returns the current element's value.
// Does not modify the state of the iterator.
func (iterator *Iterator) Value() interface{} {
value, _ := iterator.heap.list.Get(iterator.index)
start, end := evaluateRange(iterator.index)
if end > iterator.heap.Size() {
end = iterator.heap.Size()
}
tmpHeap := NewWith(iterator.heap.Comparator)
for n := start; n < end; n++ {
value, _ := iterator.heap.list.Get(n)
tmpHeap.Push(value)
}
for n := 0; n < iterator.index-start; n++ {
tmpHeap.Pop()
}
value, _ := tmpHeap.Pop()
return value
}
@ -109,3 +123,21 @@ func (iterator *Iterator) PrevTo(f func(index int, value interface{}) bool) bool
}
return false
}
// numOfBits counts the number of bits of an int
func numOfBits(n int) uint {
var count uint
for n != 0 {
count++
n >>= 1
}
return count
}
// evaluateRange evaluates the index range [start,end) of same level nodes in the heap as the index
func evaluateRange(index int) (start int, end int) {
bits := numOfBits(index+1) - 1
start = 1<<bits - 1
end = start + 1<<bits
return
}

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