本章讲解的是快速排序算法，快速排序有很多变种，不过基本原理是一样的。

int Partition(int *a, int low, int high){    int key = a[low];                       while (low < high) {                               while (low < high && a[high] >= key) {            high--;        }        a[low] = a[high];                               while (low < high && a[low] <= key) {            low++;        }        a[high] = a[low];                           }                       a[low] = key;    return low;                   }void QuickSort(int *a, int low, int high){    if (low < high) {        int mid = Partition(a, low, high);        QuickSort(a, low, mid-1);        QuickSort(a, mid+1, high);    }}int main(int argc, const char * argv[]){    int a[] = {3, 5, 1, 2, 5, 4};    int n = sizeof(a) / sizeof(*a);    int low = 0;    int high = n - 1;                       QuickSort(a, low, high);                       int i = 0;    for (; i < n; i++) {        printf("%d ", a[i]);    }                       return 0;}

输出：1 2 3 4 5 5