52 lines
1.2 KiB
Go
52 lines
1.2 KiB
Go
package day17
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import (
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"container/heap"
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)
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// An Item is something we manage in a priority queue.
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type Item struct {
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value PathSegmentEnd // The value of the item; arbitrary.
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// The index is needed by update and is maintained by the heap.Interface methods.
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index int // The index of the item in the heap.
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}
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// A PriorityQueue implements heap.Interface and holds Items.
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type PriorityQueue []*Item
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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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// We want Pop to give us the lowest, so i modify snippet
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return pq[i].value.score < pq[j].value.score
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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 any) {
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n := len(*pq)
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item := x.(*Item)
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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() any {
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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 // avoid memory leak
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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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// update modifies the priority and value of an Item in the queue.
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func (pq *PriorityQueue) update(item *Item, value PathSegmentEnd) {
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item.value = value
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heap.Fix(pq, item.index)
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}
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