1481.纪念品分组（水题）

#include <cstdio>
#include <iostream>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
#include <queue>
#include <vector>
#include <map>
using namespace std;
#define ll long long
const int maxn = 5100;

int n, w, p[30000+8], l, r, id[30000+8], sign[30000+8], num;

int main()
{
    scanf("%d", &w);
    scanf("%d", &n);
    num = 0;
    memset(sign, 0, sizeof(sign));
    for(int i = 0; i<n; i++)
        scanf("%d", &p[i]);
    sort(p, p+n, greater<int>());
    int d = n-1;
    for(int i = 0; i<n; i++)id[i] = i;
    for(int i = 0; i<n; i++)
    {
        if(p[i]+p[d] <= w && !sign[i])
        {
            id[i] = d;
            sign[d] = sign[i] = 1;
            d--;
            num++;
        }
        else if(p[i]+p[d] > w && !sign[i])
        {
            sign[i] = 1;
            num++;
        }
    }
    printf("%d\n", num);
    return 0;
}