快速排序

#include <iostream>
using namespace std;
int a[50001];
int qs(int s, int e)
{
int x = a[s], l = s, r = e;
if(l >= r)
return 0;
while (l < r)
    {
while(l<r && a[r]>=x) //从右向左扫描
            r--;
        a[l] = a[r];
while(l<r && a[l]<=x) //从左向右扫描
            l++;
        a[r] = a[l];
    }
    a[r] = x;
    qs(s, r-1); //对左区间递归排序
    qs(r+1, e); //对右区间递归排序
}

int main()
{
int i, n;
    cin>>n;
for(i=0; i<n; i++)
        cin>>a[i];
    qs(0,n-1);
for(i=0; i<n; i++)
        cout<<a[i]<<"";
    cout<<endl;
}

转载于:https://www.cnblogs.com/o8le/archive/2011/11/22/2258751.html