Merkkijonot

const fs = require("fs");

const input = fs.readFileSync(0, {encoding:"utf-8"}).split("\n");

const lines = parseInt(input[0]);

const mod = 1e9+7;

const strlist = [];

for(let i=1;i<=lines;i++) {
    amounts = [0,0];
    input[i].split("").forEach(e=>amounts[Number(e=="b")]++);
    strlist.push(amounts);
}
// console.log(...strlist);
let totals = strlist.reduce((v,e)=>[v[0]+e[0],v[1]+e[1]],[0,0]);
let targets = totals.map(e=>e/2);
let len = strlist.length;

// console.log(...totals);

function rec(a,b,i) {
//     console.log(a,b,i);
    if(a>targets[0]||b>targets[1]) {
        return 0;
    } else if(a==targets[0]&&b==targets[1]) {
        return 1;
    } else {
        let sum = 0;
        for(;i<len;i++) {
            sum+=rec(a+strlist[i][0],b+strlist[i][1],i+1);
        }
        return sum;
    }
}

console.log(rec(0,0,0));

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: TIME LIMIT EXCEEDED

Test 9

Group: 3

Verdict: ACCEPTED

Test 10

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 11

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 2, 3

Verdict: TIME LIMIT EXCEEDED

Test 16

Group: 3

Verdict: TIME LIMIT EXCEEDED