134A - Average Numbers - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;

const int N = 2e5+5;
typedef long long LL;
int a[N], n, sum = 0;
int b[N], t = 0;

void solve(){
	cin >> n;
	for(int i = 1; i <= n; i ++){
		scanf("%d", &a[i]);
		sum += a[i];
	}
	for(int i = 1; i <= n; i ++){
		if((sum-a[i])%(n-1) == 0 && a[i] == (sum-a[i])/(n-1))b[t++] = i;
	}
	cout << t << endl;
	for(int i = 0; i < t; i ++){
		cout << b[i] << " ";
	}
	cout << endl;
}

int main(){

	int T = 1;
//	cin >> T;
	while(T--)solve();

    return 0;
}