Question

#include <stdio.h>
#include <stdlib.h>

#define n 10

void swap(int * a , int * b);

int parent(int i){
    return  ((i+1)/2)-1;
}


int left(int i){
    return  2*(i+1)-1;
}


int right(int i){
    return  (2*(i+1)+1)-1;
}

int printHeap(int *heap, int pos){
 int i;
 for (i=0;i<pos;i++){
     printf("%d ",heap[i]);
     }
     printf("----\n");   
}

int insert(int *heap,int *pos, int value)
{
    int i=*pos;
    int tmp;
    heap[i]=value;
    (*pos)++;
    while(parent(i)>=0) {
       if(heap[parent(i)]<heap[i]){
          tmp=heap[parent(i)];
          heap[parent(i)]=heap[i];
          heap[i]=tmp;                                          
       }else{
             break;     
       }                    
       i=parent(i);
    } 

}

void deleteMax(int *heap,int *pos)
{
    int tmp;
    heap[0]=heap[*pos-1];
    (*pos)--;
    maxHeapify(heap,&pos);
}

void maxHeapify(int *heap,int *pos)
{
    int i=*pos,l=left(i),r=right(i),max;
    if (l<i && heap[l]>heap[i])
        max=l;
    else
        max=i;

    if(r<i && heap[r]>heap[max])
        max=r;

    if (max!=i)
    {
        swap(&heap[i],&heap[max]);
        maxHeapify(heap,max);
    }
}

void swap(int * a , int * b)
{
    int tmp;
    tmp=*a;
    *a=*b;
    *b=tmp;
}

int main()
{
    int heap[n];
    int pos=0;
    insert(heap,&pos, 10);
    insert(heap,&pos, 5);
    insert(heap,&pos, 15);
    insert(heap,&pos, 35);
    insert(heap,&pos, 66);
    insert(heap,&pos, 41);
    insert(heap,&pos, 42);
    insert(heap,&pos, 21);
    insert(heap,&pos, 14);
    insert(heap,&pos, 3);
    printHeap(heap,pos);
    deleteMax(heap,&pos);
    printHeap(heap,pos);
    system("PAUSE");
    return 0;
}

我有这个堆实现，我想删除最大堆（heap [0]），然后修复整个数组，首先我用最后一个元素（min）替换max heap，然后我尝试修复结构使用maxHeapify方法，但我似乎有些不对劲，任何想法？提前谢谢你！

Answer 1

你需要将maxHeapify放在这样的循环中：

void BuildMaxHeap(int* arr)
{
    for( int i =  9; i >= 0; i-- )
        maxHeapify( arr, &i );
}

void maxHeapify( int* arr, int *pos )
{

    int i = *pos;
    int left = 2 * i + 1;
    int right = 2 * i + 2;
    int largest = i;

    if( left < n && arr[ left ] > arr[ largest ] )
        largest = left;
    if( right < n && arr[ right ] > arr[ largest ] )
        largest = right;
    if( largest != i )
    {
        int temp = arr[ i ];
        arr[ i ] = arr[ largest ];
        arr[ largest ] = temp;
        maxHeapify( arr, &largest );
    }
}

删除最大堆方法

1 个答案: