Merkkijonot

input/code.cpp: In function 'int main()':
input/code.cpp:23:34: warning: comparison of integer expressions of different signedness: 'll' {aka 'long int'} and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   23 |                 for (ll j = 0; j < s.size(); j++) {
      |                                ~~^~~~~~~~~~

#include <iostream>
#include <algorithm>
#include <numeric>

typedef long ll;

using namespace std;

const ll N = 501;
const ll mod = 1e9 + 7;

ll n, asum, bsum;
ll a[N];
ll b[N];
ll d[N][N];

int main() {
	cin >> n;
	for (ll i = 0; i < n; i++) {
		string s;
		ll a2 = 0; ll b2 = 0;
		cin >> s;
		for (ll j = 0; j < s.size(); j++) {
			if (s[j] == 'a') a2++;
			else b2++;
		}
		a[i] = a2; b[i] = b2;
	}
	asum = accumulate(a, a + n, 0); bsum = accumulate(b, b + n, 0);
	if (asum % 2 == 1 || bsum % 2 == 1) {
		cout << 0;
		return 0; 
	}

	d[0][0] = 1;
	for (ll i = 0; i < n; i++) {
		for (ll j = N - 1; j >= 0; j--) {
			if (j - a[i] < 0) continue;
			for (ll k = N - 1; k >= 0; k--) {
				if (k - b[i] < 0) continue;
				if (a[i] == 0 && b[i] == 0) continue;
				d[j][k] += d[j - a[i]][k - b[i]] % mod;
			}
		}
	}
	cout << d[asum / 2][bsum / 2] % mod;
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 2, 3

Verdict: ACCEPTED

Test 6

Group: 2, 3

Verdict: ACCEPTED

Test 7

Group: 2, 3

Verdict: ACCEPTED

Test 8

Group: 2, 3

Verdict: ACCEPTED

Test 9

Group: 3

Verdict: ACCEPTED

Test 10

Group: 3

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 2, 3

Verdict: ACCEPTED

Test 16

Group: 3

Verdict: ACCEPTED