版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/tao_627/article/details/88582644
下面的例子来自Weiss的《数据结构与算法分析:c语言描述》,自己亲自敲了一遍,跑了个demo,并将结果记录下来。
binheap.h的头文件声明
//description: 使最小堆实现优先级队列
//date: 2019-03-15
#ifndef __BINHEAP_H__
#define __BINHEAP_H__
typedef int ElementType;
struct HeapStruct {
int Capacity; //最大容量
int Size; //当前大小
ElementType *Elements; //元素数组
};
typedef struct HeapStruct *PriorityQueue;
PriorityQueue Initialize(int MaxElements);
void Destroy(PriorityQueue H);
void MakeEmpty(PriorityQueue H);
int IsEmpty(PriorityQueue H);
int IsFull(PriorityQueue H);
void Insert(ElementType X, PriorityQueue H);
ElementType DeleteMin(PriorityQueue H);
ElementType FindMin(PriorityQueue H);
#endif
binheap.c源码文件
#include "binheap.h"
#include <stdio.h>
#include <stdlib.h>
#define MinData (-32767)
#define MinPQSize (10)
PriorityQueue
Initialize(int MaxElements){
PriorityQueue H;
if(MaxElements < MinPQSize){
printf("Priority queue size is too small");
exit(-1);
}
H = malloc(sizeof(struct HeapStruct));
if(H == NULL){
printf("failed to alloc memory space for HeapStruct");
exit(-1);
}
/* allocate the array plus one extra for sentinel */
H->Elements = malloc( (MaxElements+1) * sizeof(ElementType));
if(H->Elements == NULL){
printf("failed to allocate memory for Elements array");
exit(-1);
}
H->Capacity = MaxElements;
H->Size = 0;
H->Elements[0] = MinData; //此处设置哨兵
return H;
}
void
Destroy(PriorityQueue H){
free(H->Elements);
free(H);
}
void
MakeEmpty(PriorityQueue H){
H->Size = 0;
}
void
Insert(ElementType X, PriorityQueue H){
int i;
if(IsFull(H)){
printf("Priority queue is full");
return;
}
//从尾部向头部检查
for(i=++H->Size; H->Elements[i/2]>X; i/=2){
H->Elements[i] = H->Elements[i/2];
}
H->Elements[i] = X;
}
ElementType
DeleteMin(PriorityQueue H){
int i,Child;
ElementType MinElement, LastElement;
if(IsEmpty(H)){
printf("FATAL: Priority queue is empty");
return H->Elements[0];
}
MinElement = H->Elements[1];
LastElement = H->Elements[H->Size--];
for(i=1; i * 2 <= H->Size; i=Child){
/*Find smaller child*/
Child = i * 2;
if(Child != H->Size && H->Elements[Child+1] < H->Elements[Child])
Child++;
/*Percolate one level */
//此时最后一个元素已经在堆顶部了,头部与最后一个元素交换过了
if(LastElement > H->Elements[Child])
H->Elements[i] = H->Elements[Child];
else
break;
}
H->Elements[i] = LastElement;
return MinElement;
}
ElementType
FindMin(PriorityQueue H){
if(!IsEmpty(H))
return H->Elements[1];
printf("FATAL: Priority queue is Empty");
return H->Elements[0];
}
int
IsEmpty(PriorityQueue H){
return H->Size == 0;
}
int
IsFull(PriorityQueue H){
return H->Size == H->Capacity;
}
//=================================
int main(){
int i, NUM=30;
PriorityQueue pq = Initialize(NUM);
for(i=0; i<NUM; i++)
Insert(i, pq);
while(!IsEmpty(pq)){
i = DeleteMin(pq);
printf("%d\n", i);
}
Destroy(pq);
return 0;
}
下面是运行图示: