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// Package priority provides priority queue.
package priority
import (
"container/heap"
)
// An Item is something we manage in a priority queue.
type Item struct {
Value string // The value of the item; arbitrary.
Priority int64 // The priority of the item in the queue.
// The index is needed by update and is maintained by the heap.Interface methods.
index int // The index of the item in the heap.
}
// A Queue implements heap.Interface and holds Items.
type Queue []*Item
// Len ...
func (pq Queue) Len() int {
return len(pq)
}
// Less ...
func (pq Queue) Less(i, j int) bool {
return pq[i].Priority < pq[j].Priority
}
// Swap ...
func (pq Queue) Swap(i, j int) {
pq[i], pq[j] = pq[j], pq[i]
pq[i].index = i
pq[j].index = j
}
// Push value into queue.
func (pq *Queue) Push(x interface{}) {
n := len(*pq)
item := x.(*Item)
item.index = n
*pq = append(*pq, item)
}
// Pop value from queue.
func (pq *Queue) Pop() interface{} {
old := *pq
n := len(old)
item := old[n-1]
item.index = -1 // for safety
*pq = old[0 : n-1]
return item
}
// MakeQueue allows to create priority queue.
func MakeQueue() Queue {
pq := make(Queue, 0)
heap.Init(&pq)
return pq
}
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