堆排序算法

#include <string.h>
#include <stdio.h>

void Swap(int * a, int i, int j)
{
    int temp = a[i];
    a[i] = a[j];
    a[j] = temp;
}

void Heapify(int * a, int start, int end)
{
    int index;
    if (2 * start + 2 <= end) {
        index = a[2 * start + 1] > a[2 * start + 2] ? (2 * start + 1) : (2 * start + 2);
        if (a[index] > a[start]) {
            Swap(a, index, start);
            Heapify(a, index, end);
        }
    } else if (2 * start + 1 == end) {
        if (a[2 * start + 1] == a[start]) {
            Swap(a, 2 * start + 1, start);
        }
    }
}

void HeapSort(int * a, int n)
{
    int i;
    for (i = (n - 1) / 2; i >= 0; --i) {
        Heapify(a, i, n - 1);
    }
    for (i = n - 1; i >= 1; --i) {
        Swap(a, i, 0);
        Heapify(a, 0, i - 1);
    }
}

void Print(int * a, int n)
{
    int i;
    for (i = 0; i < n; ++i) {
        printf("%3d", a[i]);
    }
    printf("\n");
}


int main()
{
    int a[10] = {1, 9, 8, 7, 3, 5, 6, 2, 0, 4};
    Print(a, 10);
    HeapSort(a, 10);
    Print(a, 10);

    return 0;
}