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