C語言堆排序問題排查

先上代碼

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

void printf_array(int a[], int length)
{
    int i = 0;
    printf("array element:\n");
    for (i = 0; i < length; i++) {
        printf("%d\t",a[i]);
    }
    printf("\n");
}

void perDown(int a[], int parent, int length)
{
    int temp = a[parent];

    int child = 2 * parent + 1;
    while (child < length) {
        if(child + 1 < length && a[child+1] > a[child]) {//獲取較大的兒子節點
            child++;
        }

        if(a[child] > temp) {
            a[parent] = a[child];

            parent = child;
            child = parent * 2 + 1;
        } else {//跳出循環
            //a[parent] = temp;//爲何放在這裏很差使呢？
            //懷疑編譯器進行了內部優化致使此問題，放在這裏和放在while體外，原則上是同樣的意思
            break;
        }
    }
    a[parent] = temp;
    printf_array(a, length);
}
//構建大根堆
void build_big_heap(int a[], int length)
{
    int i = 0 ;
    for (i = (length - 2) / 2; i >= 0; i--) {
        perDown(a, i, length);
    }
}

void heap_sort_increasing(int a[], int length)
{
    int i = 0;
    int temp = 0;
    build_big_heap(a, length);
    printf("=========================================\n");
    //去掉堆頭，從新排序
    for (i = length - 1; i > 0; i--) {
        temp = a[i];
        a[i] = a[0];
        a[0] = temp;
        perDown(a, 0, i);
    }
}

int main()
{
    int array[] = {4,2,5,1,7,3};
    printf_array(array, 6);
    heap_sort_increasing(array, 6);
    printf_array(array, 6);
    return 0 ;
}