快排

class QuickSort {public:    void quickSort_(int *A,int l,int r){        if(l<r){            int i=l;            int j=r;            int x=A[l];            while(i<j){                    //cout<<i<<" "<<j<<endl;                while(i<j && A[j]>x){                    j--;                }                if(i<j){                    A[i]=A[j];                }                while(i<j && x>=A[i]){                    i++;                }                if(i<j){                    A[j]=A[i];                }            }            A[i]=x;            quickSort_(A,l,i-1);            quickSort_(A,i+1,r);        }    }    int* quickSort(int* A, int n) {        // write code here        int l=0,r=n-1;        quickSort_(A,l,r);        return A;    }};