First commit

heap.go

@@ -0,0 +1,103 @@
+package common
+
+import (
+	"container/heap"
+)
+
+type Comparable interface {
+	Less(o interface{}) bool
+}
+
+//-----------------------------------------------------------------------------
+
+/*
+Example usage:
+	h := NewHeap()
+
+	h.Push(String("msg1"), 1)
+	h.Push(String("msg3"), 3)
+	h.Push(String("msg2"), 2)
+
+	fmt.Println(h.Pop())
+	fmt.Println(h.Pop())
+	fmt.Println(h.Pop())
+*/
+
+type Heap struct {
+	pq priorityQueue
+}
+
+func NewHeap() *Heap {
+	return &Heap{pq: make([]*pqItem, 0)}
+}
+
+func (h *Heap) Len() int64 {
+	return int64(len(h.pq))
+}
+
+func (h *Heap) Push(value interface{}, priority Comparable) {
+	heap.Push(&h.pq, &pqItem{value: value, priority: priority})
+}
+
+func (h *Heap) Peek() interface{} {
+	if len(h.pq) == 0 {
+		return nil
+	}
+	return h.pq[0].value
+}
+
+func (h *Heap) Update(value interface{}, priority Comparable) {
+	h.pq.Update(h.pq[0], value, priority)
+}
+
+func (h *Heap) Pop() interface{} {
+	item := heap.Pop(&h.pq).(*pqItem)
+	return item.value
+}
+
+//-----------------------------------------------------------------------------
+
+///////////////////////
+// From: http://golang.org/pkg/container/heap/#example__priorityQueue
+
+type pqItem struct {
+	value    interface{}
+	priority Comparable
+	index    int
+}
+
+type priorityQueue []*pqItem
+
+func (pq priorityQueue) Len() int { return len(pq) }
+
+func (pq priorityQueue) Less(i, j int) bool {
+	return pq[i].priority.Less(pq[j].priority)
+}
+
+func (pq priorityQueue) Swap(i, j int) {
+	pq[i], pq[j] = pq[j], pq[i]
+	pq[i].index = i
+	pq[j].index = j
+}
+
+func (pq *priorityQueue) Push(x interface{}) {
+	n := len(*pq)
+	item := x.(*pqItem)
+	item.index = n
+	*pq = append(*pq, item)
+}
+
+func (pq *priorityQueue) Pop() interface{} {
+	old := *pq
+	n := len(old)
+	item := old[n-1]
+	item.index = -1 // for safety
+	*pq = old[0 : n-1]
+	return item
+}
+
+func (pq *priorityQueue) Update(item *pqItem, value interface{}, priority Comparable) {
+	item.value = value
+	item.priority = priority
+	heap.Fix(pq, item.index)
+}