Merkkijonot

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define N 550
#define M 1000000007
 
int n,a,b,T[N][2],f[N][N],A,B;
string s;
 
int main(){
	cin.tie(0)->sync_with_stdio(0);
	cin>>n;
	for(int i=0;i<n;++i){
		cin>>s;
		a=b=0;
		for(int c:s){
			if(c=='a') ++a;
			else ++b;
		}
		T[i][0]=a;
		T[i][1]=b;
		A+=a;
		B+=b;
	}
	if(A&1||B&1){
		cout<<"0\n";
		return 0;
	}
 
	for(int i=0;i<n;++i){
		int aa=T[i][0],bb=T[i][1];
		for(int a=A;a>=aa;--a){
			for(int b=B;b>=bb;--b){
				f[a][b]=(f[a][b]+f[a-aa][b-bb])%M;
			}
		}
		f[aa][bb]=(f[aa][bb]+1)%M;
	}
	cout<<f[A/2][B/2]<<'\n';
}

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