51nod 独木舟问题

题目：http://www.51nod.com/contest/problem.html#!problemId=1432

证明：http://blog.youkuaiyun.com/hfutxern/article/details/50654795

整天想着一些骚操作，才发现while已经不会用了=_=

#include<cstdio>
#include<queue>
#include<iostream>
#include<vector>
#include<map>
#include<cstring>
#include<string>
#include<set>
#include<stack>
#include<algorithm>
#define cle(a) memset(a,0,sizeof(a))
#define inf(a) memset(a,ox3f,sizeof(a))
#define ll long long
#define Rep(i,a,n) for(int i=a;i<=n;i++)
using namespace std;
const int INF = ( 2e9 ) + 2;
const int maxn = 1e4+10;
int a[maxn];
int main()
{
	int n,m;
	scanf("%d%d",&n,&m);
	for(int i=0;i<n;i++)
	scanf("%d",&a[i]);
	int i=0,j=n-1;
	ll ans=0;
	sort(a,a+n); 
	while(i<=j)
	{
		if(i==j)
		{
			ans++;
			break;
		}
		else if(a[i]+a[j]<=m)
		{
			ans++;
			j--;
			i++;
		}
		else if(a[i]+a[j]>m)
		{
			j--;
			ans++;
		}
	}
	printf("%lld\n",ans);
}