75 lines
1.9 KiB
Go
75 lines
1.9 KiB
Go
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package queue
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import (
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"container/heap"
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)
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// PriorityQueueItem is an interface that represents items in a PriorityQueue.
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// Users of PriorityQueue will need to define a Less function such that
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// PriorityQueue will be able to use that to build and restore an underlying
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// heap.
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type PriorityQueueItem interface {
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Less(other PriorityQueueItem) bool
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}
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type priorityQueue []PriorityQueueItem
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// Len returns the length of the priorityQueue.
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func (pq priorityQueue) Len() int { return len(pq) }
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// Less is used to order PriorityQueueItem items in the queue.
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func (pq priorityQueue) Less(i, j int) bool {
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return pq[i].Less(pq[j])
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}
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// Swap swaps two items in the priorityQueue. Swap is used by heap.Interface.
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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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}
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// Push adds a new item the the priorityQueue.
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func (pq *priorityQueue) Push(x interface{}) {
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item := x.(PriorityQueueItem)
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*pq = append(*pq, item)
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}
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// Pop removes the top item from the priorityQueue.
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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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old[n-1] = nil
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*pq = old[0 : n-1]
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return item
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}
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// Priority wrap a standard heap in a more object-oriented structure.
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type PriorityQueue struct {
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queue priorityQueue
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}
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// Len returns the length of the queue.
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func (pq *PriorityQueue) Len() int {
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return len(pq.queue)
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}
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// Empty returns true if the queue is empty.
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func (pq *PriorityQueue) Empty() bool {
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return len(pq.queue) == 0
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}
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// Push adds an item to the priority queue.
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func (pq *PriorityQueue) Push(item PriorityQueueItem) {
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heap.Push(&pq.queue, item)
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}
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// Pop removes the top most item from the queue.
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func (pq *PriorityQueue) Pop() PriorityQueueItem {
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return heap.Pop(&pq.queue).(PriorityQueueItem)
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}
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// Top returns the top most item from the queue without removing it.
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func (pq *PriorityQueue) Top() PriorityQueueItem {
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return pq.queue[0]
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}
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