使用最小堆使用优先级队列(c语言版本)

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 
#include 

#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

下面是运行图示：