1121B - Mike and Children - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;
int main() {
    std::ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int n; cin >>n; int arr[n];
    int frq[200001]={0};
    int sum=0,mx=0;
    for (int i = 0; i <n ; ++i) {
        cin >> arr[i];
    }
    for (int i = 0; i <n-1 ; ++i) {
        for (int j = i+1; j <n ; ++j) {
            sum=arr[i]+arr[j];
            frq[sum]++;
            mx=max(frq[sum],mx);
        }
    }
    cout << mx;



}