poj 3663 Costume Party

Costume Party

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 8495		Accepted: 3279

Description

It's Halloween! Farmer John is taking the cows to a costume party, but unfortunately he only has one costume. The costume fits precisely two cows with a length of S (1 ≤ S ≤ 1,000,000). FJ has N cows (2 ≤ N ≤ 20,000) conveniently numbered 1..N; cow i has length L_i (1 ≤ L_i ≤ 1,000,000). Two cows can fit into the costume if the sum of their lengths is no greater than the length of the costume. FJ wants to know how many pairs of two distinct cows will fit into the costume.

Input

* Line 1: Two space-separated integers: N and S
* Lines 2..N+1: Line i+1 contains a single integer: L_i

Output

* Line 1: A single integer representing the number of pairs of cows FJ can choose. Note that the order of the two cows does not matter.

Sample Input

4 6
3
5
2
1

Sample Output

4

#include<iostream>
#include<algorithm>
int comp(const void *a,const void *b)
{
    return *(int *)a-*(int *)b;
}
using namespace std;
int main()
{
    int n,s;
    int i,j;
    int sum;
    int cows[20000];
    cin>>n;
    cin>>s;
    for(i=0;i<n;i++)
        cin>>cows[i];
    qsort(cows,n,sizeof(cows[0]),comp);
    sum=0;
    for(i=0;i<n;i++)
    {
        for(j=i+1;j<n;j++)
        {
            if(cows[i]+cows[j]<=s)
                sum++;
            else
                break;
        }
    }
    cout<<sum<<endl;
    return 0;
}