initial import

core/stat/topk.go

@@ -0,0 +1,45 @@
+package stat
+
+import "container/heap"
+
+type taskHeap []Task
+
+func (h *taskHeap) Len() int {
+	return len(*h)
+}
+
+func (h *taskHeap) Less(i, j int) bool {
+	return (*h)[i].Duration < (*h)[j].Duration
+}
+
+func (h *taskHeap) Swap(i, j int) {
+	(*h)[i], (*h)[j] = (*h)[j], (*h)[i]
+}
+
+func (h *taskHeap) Push(x interface{}) {
+	*h = append(*h, x.(Task))
+}
+
+func (h *taskHeap) Pop() interface{} {
+	old := *h
+	n := len(old)
+	x := old[n-1]
+	*h = old[0 : n-1]
+	return x
+}
+
+func topK(all []Task, k int) []Task {
+	h := new(taskHeap)
+	heap.Init(h)
+
+	for _, each := range all {
+		if h.Len() < k {
+			heap.Push(h, each)
+		} else if (*h)[0].Duration < each.Duration {
+			heap.Pop(h)
+			heap.Push(h, each)
+		}
+	}
+
+	return *h
+}