good_array.cpp

#include <iostream> 
#include <vector>
#include <algorithm>

using namespace std;

vector<long int> v;
vector<long int> result;

bool descSort(long int a, long int b){
	return a > b;
}

long long totalSum(){
	long long value  = 0;

	for (long long i = 0; i < v.size(); ++i){
		value += v[i];
	}

	return value;
}

void findSubArr(long long value){
	long long subTotal;

	for (long long i = 0; i < v.size(); ++i){
		subTotal = value - v[i];

		for (long long j = 0; j < v.size(); ++j){
			if(j == i){
				continue;
			}
			if(subTotal - v[j] == v[i]){
				// bo vi tri nay ok
				result.push_back(j);
			}
		}
	}

	cout << result.size() << endl;
	for (long long i = 0; i < result.size(); ++i){
		cout << (result[i] +1) << " ";
	}
}

int main(){
	long long n;
	long int a;

	cin >> n;

	for (long long i = 0; i < n; ++i){
		cin >> a;
		v.push_back(a);

	}

	//sort(v.begin(), v.end(), descSort);
	findSubArr(totalSum());

	return 0;
}