(Relax ST1.20)POJ 3663 Costume Party(贪心+剪枝)

/*
* POJ_3663.cpp
*
*  Created on: 2013年11月26日
*      Author: Administrator
*/
#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

const int maxn = 20005;
int a[maxn];

int main(){
int n,s;
while(scanf("%d%d",&n,&s)!=EOF){
int i;
for(i = 0 ; i < n ; ++i){
scanf("%d",&a[i]);
}

sort(a,a+n);

int count = 0;
int j;
for(i = 0 ; i < n-1 ; ++i){
if(a[i] > s){//剪枝,不剪枝的话会TLE
break;
}
for(j = i+1 ; j < n ; ++j){
if(a[i] + a[j] <= s){
count++;
}
}
}

printf("%d\n",count);
}

return 0;
}