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