Merkkijonot

input/code.cpp: In function 'int check(int, std::pair<int, int>)':
input/code.cpp:16:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |     if(i == pairs.size())
      |        ~~^~~~~~~~~~~~~~~

#include <iostream>
#include <string>
#include <vector>
#include <tuple>
#include <unordered_map>

std::vector<std::pair<int, int>> pairs;
int mem[500*500*500];

// This is O(2^n) algo
int check(int i, std::pair<int, int> val)
{
    if(val.first == 0 && val.second == 0)
        return 1;

    if(i == pairs.size())
        return 0;

    auto a = mem[i*500*500+val.first*500 +val.second];
    if(a != -1)
        return a;

    std::pair<int, int> test;
    test.first = val.first - pairs[i].first;
    test.second = val.second - pairs[i].second;
    
    int sum = 0;
    if(test.second >= 0 && test.first >= 0)
        sum += check(i + 1, test) % 1000000007;
    sum += check(i + 1, val) % 1000000007;

    mem[i*500*500+val.first*500 +val.second] = sum;
    return sum;
}

int main()
{
    int n;
    std::cin >> n;

    // Sub sum problem except sketchy???? so best case O(nm) ?????
    // Only half has to be cheked
    // pari (count of a, count of b) for 1 part

    pairs.resize(n);
    int totalA = 0;
    int totalB = 0;

    for(int i = 0; i < n; i++)
    {
        std::string str;
        std::cin >> str;

        // Count the intsances of a
        for(auto c : str)
        {
            if(c == 'a')
            {
                totalA++;
                pairs[i].first++;
            }
            else {
                totalB++;
                pairs[i].second++;
            }
        }
    }

    for(auto& a : mem)
        a = -1;

    //mem = { -1 };
    if(totalA % 2 == 0 && totalB % 2 == 0)
        std::cout << check(0, { totalA/2, totalB/2 }) << "\n";
    else
        std::cout << 0 << "\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: WRONG ANSWER

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 2, 3

Verdict: WRONG ANSWER

Test 16

Group: 3

Verdict: WRONG ANSWER