56282db30a
This commit introduces PriorityQueue, which is a general, heap based priority queue, and PriorityQueueItem which is an interface that concrete priority queue items must implement. This implementation is encapsulated, users do not need to use any other package for full functionality. PriorityQueue exports the usual public methids: Push, Pop, Top, Empty and Len. For full documentaton consult the priority_queue.go, for usage: priority_queue_test.go
75 lines
1.9 KiB
Go
75 lines
1.9 KiB
Go
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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