[백준 20501] Facebook

그냥 bitset만 알면 된다
 

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#include <iostream>
#include <vector>
#include <bitset>

#define SIZE 2000

using namespace std;

bitset<SIZE> bits;
vector<bitset<SIZE>> arr;

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	
	int N, Q, a ,b;
	cin >> N;
	for (int i = 0; i < N; i++) {
		cin >> bits;
		arr.push_back(bits);
	}
	
	cin >> Q;
	for (int i = 0; i < Q; i++) {
		cin >> a >> b;
		cout << (arr[a - 1] & arr[b - 1]).count() << "\n";
	}

	return 0;
}