快速排序（双向扫描）

#include<iostream>
#include<vector>
#include<algorithm>
#include<cstdio>
#include<queue>
#include<stack>
#include<string>
#include<map>
#include<set>
#include<cmath>
#include<cassert>
#include<cstring>
#include<iomanip>
using namespace std;
#define FOR(i,a,b)      for( int i = (a) ; i <= (b) ; i ++)
#define FF(i,a)        for( int i = 0 ; i < (a) ; i ++)
#define FFD(i,a,b)      for( int i = (a) ; i >= (b) ; i --)
#define S64(a)          scanf(in64,&a)
#define sf(a)           scanf("%d",&a)
#define LL(a)           ((a)<<1)
#define RR(a)           (((a)<<1)+1)
#define PB              push_back
#define PF              push_front
#define X               first
#define Y               second
#define CL(Q)           while(!Q.empty())Q.pop()
#define MM(name,what)   memset(name,what,sizeof(name))
#define MC(a,b)         memcpy(a,b,sizeof(b))
#define MAX(a,b)        ((a)>(b)?(a):(b))
#define MIN(a,b)        ((a)<(b)?(a):(b))
#define read            freopen("in.txt","r",stdin)
#define write           freopen("out.txt","w",stdout)



#define MAX_SIZE 10000+1
int num[MAX_SIZE];
int temp[MAX_SIZE];

int partion(int num[],int left,int right)
{
	int i,j,index,exchage;
	index = num[left];
	i=left;
	j=right;
	while (i<j) // 双向扫描算法
	{
		while(num[i]<=index&&i<right)
		i++;
	
		while(num[j]>=index&&j>left)
			j--;
		
		if(i>=j)break;
		swap(num[i],num[j]);
	}

	 swap(num[left],num[j]);// 从小到大排序注意是 交换 j 和 index 位置！

	return j;
}
void quick_sort(int num[],int lo,int hi)
{
	if (lo<hi)
	{
		int x = partion(num,lo,hi);
		quick_sort(num,lo,x-1);
		quick_sort(num,x+1,hi);

	}
}
int main()
{
//	freopen("data1.in","r",stdin);
	MM(num,0);
	int n,i,j;
	while (~sf(n))
	{
		for (i=0;i<n;i++)
			sf(num[i]);
		quick_sort(num,0,n-1);
	 for(i=0;i<n;i++)
		 printf("%d\n",num[i]);
	}
	return 0;
}