蒟蒻用的是贪心，大佬不喜勿碰

#include <bits/stdc++.h>
using namespace std;
int w, ans, a[30005], l, r, n;
int main()
{
    cin >> w >> n;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    sort (a + 1, a + n + 1);
    l = 1, r = n;
    while (l <= r)
    {
        if (a[l] + a[r] <= w)
        {
            l++;
            r--;
            ans++;
        }
        else
        {
            r--;
            ans++;
        }
    }
    cout << ans << endl;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int n,maxx,sum,num,a[100005],l,r;
int main(){
    cin>>maxx>>n;
    for(int i=0;i<n;i++)cin>>a[i];
    sort(a,a+n);
    r=n-1;
    while(n>0){
        if(a[l]+a[r]>maxx){
            r--;
            num++;
            n--;
        }
        else{
            r--;
            l++;
            num++;
            n-=2;
        }
    }
    cout<<num;
    return 0;
} // 已AC

#include <bits/stdc++.h> using namespace std; vector<int> qwq[1000010]; int n,m,a,x,y; int main() { cin >> n; for (int i = 0; i < n; i++) { cin >> x >> y; qwq[x].push_back(y); } cin >> m; for (int i = 1; i <= m; i++) { cin >> a; int len = qwq[a].size(); if (len == 0) cout << endl; else if (len % 2 == 0) cout<<qwq[a][len/2-1]<<" "<<qwq[a][len/2]<<endl; else cout << qwq[a][len/2] << endl; } return 0; }//已AC