快速排序

分两部分实现，函数sort（）负责选定区间，函数Qsort（）负责给选定区间的数值分大小

class QuickSort {public:    int Qsort(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 sort(int* A,int left,int right){        if(left < right){            int key = Qsort(A,left,right);            sort(A,left,key-1);            sort(A,key+1,right);        }            }    int* quickSort(int* A, int n) {        // write code here        sort(A,0,n-1);               return A;    }};