77 lines
1.9 KiB
Go
77 lines
1.9 KiB
Go
package kheap
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import (
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"container/heap"
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)
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// HeapItem is an interface type implemented by objects stored in the ScoreHeap
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type HeapItem interface {
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Data() interface{} // The data object
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Score() float64 // Score to use as the sort criteria
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}
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// A ScoreHeap implements heap.Interface and is a min heap
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// that keeps the top K elements by Score. Push can be called
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// with an arbitrary number of values but only the top K are stored
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type ScoreHeap struct {
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items []HeapItem
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capacity int
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}
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func NewScoreHeap(capacity uint32) *ScoreHeap {
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return &ScoreHeap{capacity: int(capacity)}
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}
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func (pq ScoreHeap) Len() int { return len(pq.items) }
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func (pq ScoreHeap) Less(i, j int) bool {
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return pq.items[i].Score() < pq.items[j].Score()
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}
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func (pq ScoreHeap) Swap(i, j int) {
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pq.items[i], pq.items[j] = pq.items[j], pq.items[i]
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}
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// Push implements heap.Interface and only stores
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// the top K elements by Score
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func (pq *ScoreHeap) Push(x interface{}) {
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item := x.(HeapItem)
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if len(pq.items) < pq.capacity {
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pq.items = append(pq.items, item)
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} else {
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// Pop the lowest scoring element if this item's Score is
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// greater than the min Score so far
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minIndex := 0
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min := pq.items[minIndex]
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if item.Score() > min.Score() {
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// Replace min and heapify
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pq.items[minIndex] = item
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heap.Fix(pq, minIndex)
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}
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}
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}
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// Push implements heap.Interface and returns the top K scoring
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// elements in increasing order of Score. Callers must reverse the order
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// of returned elements to get the top K scoring elements in descending order
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func (pq *ScoreHeap) Pop() interface{} {
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old := pq.items
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n := len(old)
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item := old[n-1]
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pq.items = old[0 : n-1]
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return item
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}
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// GetItemsReverse returns the items in this min heap in reverse order
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// sorted by score descending
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func (pq *ScoreHeap) GetItemsReverse() []interface{} {
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ret := make([]interface{}, pq.Len())
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i := pq.Len() - 1
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for pq.Len() > 0 {
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item := heap.Pop(pq)
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ret[i] = item
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i--
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}
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return ret
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}
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