/
maxheap.go
65 lines (55 loc) · 1.6 KB
/
maxheap.go
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package test
import (
"container/heap"
)
// An Item is something we manage in a weight queue.
type Item struct {
value string // The value of the item; arbitrary.
weight float64 // The weight 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 PriorityQueue implements heap.Interface and holds Items.
type PriorityQueue []*Item
func (pq PriorityQueue) Len() int { return len(pq) }
func (pq PriorityQueue) Less(i, j int) bool {
// We want Pop to give us the smallest, not highest, weight so we use smaller than here.
return pq[i].weight < pq[j].weight
}
func (pq PriorityQueue) Swap(i, j int) {
pq[i], pq[j] = pq[j], pq[i]
pq[i].index = i
pq[j].index = j
}
// Push adds an item to the priority q
func (pq *PriorityQueue) Push(x interface{}) {
n := len(*pq)
item := x.(*Item)
item.index = n
*pq = append(*pq, item)
}
// Pop removes the smallest item from the priority q
func (pq *PriorityQueue) Pop() interface{} {
old := *pq
n := len(old)
item := old[n-1]
old[n-1] = nil // avoid memory leak
item.index = -1 // for safety
*pq = old[0 : n-1]
return item
}
// Find finds an item with the given value and returns it. Nil is nothing is found
func (pq PriorityQueue) Find(value string) *Item {
for _, item := range pq {
if item.value == value {
return item
}
}
return nil
}
// update modifies the weight and value of an Item in the queue.
func (pq *PriorityQueue) update(item *Item, value string, weight float64) {
item.value = value
item.weight = weight
heap.Fix(pq, item.index)
}