堆排序

https://www.jianshu.com/p/938789fde325

//
//  main.c
//
//  Created by 柏超曾 on 3/20/18.
//  Copyright © 2018 柏超曾. All rights reserved.
//

#include <stdio.h>

//给定父节点的索引，得到左子节点的索引
#define LeftChild(i) (2*(i)+1)
//元素下沉方法
void PercDown(int A[], int i, int N)
{
    //子节点的索引号
    int child;
    //存储当前父节点元素的临时变量
    //(注：每一个节点都可以看作是其子树的根节点)
    int tmp;
    
    for (tmp = A[i]; LeftChild(i)<N; i = child)
    {
        child = LeftChild(i);
        //挑选出左、右子节点中较大者
        if (child != N-1 && A[child+1]>A[child])
        {
            child++;
        }
        //比较当前父节点与较大子节点
        if (A[i]<A[child])
        {
            //交换当前父节点处的元素值与较大子节点的元素值
            tmp= A[i];
            A[i] = A[child];
            A[child] = tmp;
        }
        else
        {
            break;
        }
        
    }
}


//交换两个元素的位置
void Swap(int *num1, int * num2)
{
    int tmp = *num1;
    *num1 = *num2;
    *num2 = tmp;
}
//堆排序
void HeapSort(int A[], int N)
{
    int i;
    //步骤一：创建大根堆
    for (i  = N/2;  i>=0; i--)
    {
        PercDown(A, i, N);
        
    }
    //步骤二：调整大根堆
    for ( i = N-1; i > 0; i--)
    {
        //首尾交换
        Swap(&A[0], &A[i]);
        //元素下沉
        PercDown(A, 0, i);
    }
}



//主函数
int main(int argc, const char * argv[])

{
    int A[6] = {4,5,3,2,6,1};
    HeapSort(A, 6);
    
    
    for(int i = 0; i < 6;i ++)
    {
        printf("%d ", A[i]);
    }

    
    return 0;
}