Merkkijonot

input/code.cpp: In function 'void solve()':
input/code.cpp:31:25: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |       for (int j = 0; j < s.size(); ++j) {
      |                       ~~^~~~~~~~~~

#include<bits/stdc++.h>


using namespace std;

void init_code(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #endif 
}

bool cmp (pair<int, int> a, pair<int, int> b) {
   return a.second < b.second;
}

const int mod = 1e9 + 7;

void solve() {
   int n;
   cin >> n;

   int suma = 0, sumb = 0; 
   vector<pair<int, int>> v(n);
   for (int i = 0; i < n; ++i) {
      string s;
      cin >> s;
      int a = 0, b = 0;
      for (int j = 0; j < s.size(); ++j) {
         a += (s[j] == 'a');
         b += (s[j] == 'b');
      }
      v[i] = {a, b};
      suma += a;
      sumb += b;
   }

   // subtask 1
   int mn = (1 << n);
   int ans = 0;
   for (int i = 1; i < mn; ++i) {
      //cout << i << ' ';
      int cura = 0, curb = 0;
      int x = i, cnt = 0;
      while (x > 0) {
         int t = x % 2;
         if (t) { 
            cura += v[cnt].first; curb += v[cnt].second;
         }
         x >>= 1;
         cnt++;
         //cout << t;
      }
      if (suma == cura * 2 && sumb == curb * 2) {
         ans++;
      } 
      //cout << '\n';
   }
   cout << (ans * 2) % mod << '\n';
}

signed main() {
   init_code();
   int t = 1; 
   //cin >> t;
   while(t--){
      solve();
   }
   return 0;
}

/*
cubbli-guest@dx5-cs-b221-09:~$ cd Code
cubbli-guest@dx5-cs-b221-09:~/Code$ ls
code  code.cpp  input.txt  output.txt
cubbli-guest@dx5-cs-b221-09:~/Code$ g++ code.cpp -o code
cubbli-guest@dx5-cs-b221-09:~/Code$ ./code
Segmentation fault (core dumped)
cubbli-guest@dx5-cs-b221-09:~/Code$ 

double l = 0, r = sqrt(a), m = 0;
   for (int i = 0; i < 120; ++i) {
      m = (r + l) / 2;
      if ((m + 1) * (a / m + 1) < b) {
         r = m;
      } else {
         l = m;
      }
   }

   if ((r + 1) * (a / r + 1) == b) {
      cout << "YES" << '\n';
   } else {
      cout << "NO" << '\n';
   }
*/

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 3

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 2, 3

Verdict: ACCEPTED

Test 6

Group: 2, 3

Verdict: WRONG ANSWER

Test 7

Group: 2, 3

Verdict: WRONG ANSWER

Test 8

Group: 2, 3

Verdict: WRONG ANSWER

Test 9

Group: 3

Verdict: ACCEPTED

Test 10

Group: 3

Verdict: WRONG ANSWER

Test 11

Group: 3

Verdict: WRONG ANSWER

Test 12

Group: 3

Verdict: WRONG ANSWER

Test 13

Group: 3

Verdict: WRONG ANSWER

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 2, 3

Verdict: WRONG ANSWER

Test 16

Group: 3

Verdict: WRONG ANSWER