Golang Container.Heap 使用

type hp []*ListNode 
func (h hp) Len() int { return len(h) } 
func (h hp) Less(i, j int) bool { return h[i].Val < h[j].Val } 
func (h hp) Swap(i, j int) { h[i], h[j] = h[j], h[i] } 
func (h *hp) Push(v any) { 
	*h = append(*h, v.(*ListNode)) 
} 
func (h *hp) Pop() any { 
	a := *h
	v := a[len(a)-1]
	*h = a[:len(a)-1]
	return v 
} 

源码

// Copyright 2009 The Go Authors. All rights reserved.  
// Use of this source code is governed by a BSD-style  
// license that can be found in the LICENSE file.  
  
// Package heap provides heap operations for any type that implements  
// heap.Interface. A heap is a tree with the property that each node is the  
// minimum-valued node in its subtree.  
//  
// The minimum element in the tree is the root, at index 0.  
//  
// A heap is a common way to implement a priority queue. To build a priority  
// queue, implement the Heap interface with the (negative) priority as the  
// ordering for the Less method, so Push adds items while Pop removes the// highest-priority item from the queue. The Examples include such an  
// implementation; the file example_pq_test.go has the complete source.  
//  
package heap  
  
import "sort"  
  
// The Interface type describes the requirements// for a type using the routines in this package.  
// Any type that implements it may be used as a  
// min-heap with the following invariants (established after  
// Init has been called or if the data is empty or sorted)://  
// !h.Less(j, i) for 0 <= i < h.Len() and 2*i+1 <= j <= 2*i+2 and j < h.Len()  
//  
// Note that Push and Pop in this interface are for package heap's// implementation to call. To add and remove things from the heap,  
// use heap.Push and heap.Pop.  
type Interface interface {  
   sort.Interface  
   Push(x interface{}) // add x as element Len()  
   Pop() interface{}   // remove and return element Len() - 1.  
}  
  
// Init establishes the heap invariants required by the other routines in this package.// Init is idempotent with respect to the heap invariants// and may be called whenever the heap invariants may have been invalidated.  
// The complexity is O(n) where n = h.Len().  
func Init(h Interface) {  
   // heapify  
   n := h.Len()  
   for i := n/2 - 1; i >= 0; i-- {  
      down(h, i, n)  
   }  
}  
  
// Push pushes the element x onto the heap.// The complexity is O(log n) where n = h.Len().  
func Push(h Interface, x interface{}) {  
   h.Push(x)  
   up(h, h.Len()-1)  
}  
  
// Pop removes and returns the minimum element (according to Less) from the heap.// The complexity is O(log n) where n = h.Len().  
// Pop is equivalent to Remove(h, 0).  
func Pop(h Interface) interface{} {  
   n := h.Len() - 1  
   h.Swap(0, n)  
   down(h, 0, n)  
   return h.Pop()  
}  
  
// Remove removes and returns the element at index i from the heap.// The complexity is O(log n) where n = h.Len().  
func Remove(h Interface, i int) interface{} {  
   n := h.Len() - 1  
   if n != i {  
      h.Swap(i, n)  
      if !down(h, i, n) {  
         up(h, i)  
      }  
   }  
   return h.Pop()  
}  
  
// Fix re-establishes the heap ordering after the element at index i has changed its value.// Changing the value of the element at index i and then calling Fix is equivalent to,// but less expensive than, calling Remove(h, i) followed by a Push of the new value.// The complexity is O(log n) where n = h.Len().  
func Fix(h Interface, i int) {  
   if !down(h, i, h.Len()) {  
      up(h, i)  
   }  
}  
  
func up(h Interface, j int) {  
   for {  
      i := (j - 1) / 2 // parent  
      if i == j || !h.Less(j, i) {  
         break  
      }  
      h.Swap(i, j)  
      j = i  
   }  
}  
  
func down(h Interface, i0, n int) bool {  
   i := i0  
   for {  
      j1 := 2*i + 1  
      if j1 >= n || j1 < 0 { // j1 < 0 after int overflow  
         break  
      }  
      j := j1 // left child  
      if j2 := j1 + 1; j2 < n && h.Less(j2, j1) {  
         j = j2 // = 2*i + 2  // right child  
      }  
      if !h.Less(j, i) {  
         break  
      }  
      h.Swap(i, j)  
      i = j  
   }  
   return i > i0  
}