快速排序

找了一下以前的帖子，竟没有，补一下。

/home/a/j/nomad2:cat quicksort.c 
#include <stdio.h>

int partition(int *a, int m, int n)
{
        int low = m;
        int high = n;
        int pivot = low;
        int pvalue = a[pivot];

        while(low < high)
        {
                while(low < high && a[high] >= pvalue)
                {
                        high--;
                }
                a[low] = a[high];
                while(low < high && a[low] <= pvalue)
                {
                        low++;
                }
                a[high] = a[low];
        }
        a[low] = pvalue;
        return low;
}

void quicksort(int *a, int m, int n)
{
        int pivot;
        if ( m < n )
        {
                pivot = partition(a,m,n);
                quicksort(a, m, pivot-1);
                quicksort(a, pivot+1, n);
        }
}

int main()
{
        int a[] = {49, 38, 65, 97, 76, 13, 27, 49};
        int n = sizeof(a)/sizeof(int);
        int i = 0;
        quicksort(a, 0, n-1);

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

运行结果：

/home/a/j/nomad2:./a.out         
13 27 38 49 49 65 76 97