poj2782

简单题，先从大到小排序，然后从两端开始向中间看看能不能把右端的匹配给左端。

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
using namespace std;

#define maxn 100005

int n, m;
int f[maxn];

int cmp(int a, int b)
{
    return a > b;
}

int main()
{
    //freopen("t.txt", "r", stdin);
    scanf("%d%d", &n, &m);
    for (int i = 0; i < n; i++)
        scanf("%d", &f[i]);
    sort(f, f + n, cmp);
    int l = 0, r = n - 1;
    while (l <= r)
    {
        if (f[l] + f[r] <= m)
            r--;
        l++;
    }
    printf("%d\n", l);
    return 0;
}