快速排序算法实现

# include <iostream>
using namespace std;
void my_qsort(int arr[], int, int); 

int main()  
{
    int n;
    cin>>n;
    int *arr = new int[n];
    for(int i = 0;i < n; ++i)
        cin >> arr[i];
    my_qsort(arr, 0, n - 1);
    for(int i = 0; i < n; ++i)
        cout << arr[i]<<" ";
    cout<<endl; 
}
void my_qsort(int arr[], int l, int r) 
{
    int i, j, p,mid;
    i=l;
    j=r;
    mid=arr[(l+r)/2];
    do  
    {
        while(arr[i]<mid) i++;
        while(arr[j]>mid) j--;
        if(i<=j)
        {
            p=arr[i];
            arr[i]=arr[j];
            arr[j]=p;
            i++;
            j--; 
        }
    } while(i<=j);
    if(l<j) my_qsort(arr, l, j);
    if(i<r) my_qsort(arr, i, r);
}
/*
 * 1 6 4 2 3 mid = 4, i = 0, j = 4
 * 1 3 4 2 6 mid = 4, i = 2, j = 3
 * 1 3 2 4 6 mid = 4, i = 3, j = 2
 * 1 3 2 mid = 1, i = 0, j = 2
 * 1 2 3 mid = 1, i = 2, j = 1
 * 4 6  ...
 * result:
 * 1 2 3 4 6
 */