Judge correctness

input/code.cpp: In function 'void printmat(std::vector<std::vector<long int> >)':
input/code.cpp:25:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0; i < M.size(); i++){
                               ^
input/code.cpp:26:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
       for(int j = 0; j < M.size(); j++){
                                 ^
input/code.cpp: In function 'std::vector<std::vector<long int> > read_matrix(LL)':
input/code.cpp:37:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int j = 0; j < s.size(); j++){
                               ^

#include <iostream>
#include <string>
#include <set>
#include <vector>
#include <utility>

using namespace std;

typedef int64_t LL;

vector<LL> matmul(vector<vector<LL> > M, vector<LL> v){
  int n = v.size();
  vector<LL> ans(n);
  for(int i = 0; i < n; i++){
    LL x = 0;
    for(int j = 0; j < n; j++){
      x += M[i][j] * v[j];
    }
    ans[i] = x % 64;
  }
  return ans;
}

void printmat(vector<vector<LL> > M){
    for(int i = 0; i < M.size(); i++){
      for(int j = 0; j < M.size(); j++){
	cout << M[i][j] << " ";
      }
      cout << endl;
    }
}

vector<vector<LL> > read_matrix(LL n){
  vector<vector<LL> > M(n, vector<LL>(n));
  for(int i = 0; i < n; i++){
    string s; cin >> s;
    for(int j = 0; j < s.size(); j++){
      LL x = 0;
      if(s[j] >= 'A' && s[j] <= 'Z') x = s[j] - 'A';
      if(s[j] >= 'a' && s[j] <= 'z') x = s[j] - 'a' + 26;
      if(s[j] >= '0' && s[j] <= '9') x = s[j] - '0' + 52;
      if(s[j] == '+') x = 62;
      if(s[j] == '/') x = 63;
      M[i][j] = x;
    }
  }
  return M;
}

void solve(){
  LL n; cin >> n;
  auto A = read_matrix(n);
  auto X = read_matrix(n);
  vector<vector<LL> > A_T(n, vector<LL>(n)); // transpose
  for(int i = 0; i < n; i++){
    for(int j = 0; j < n; j++){
      A_T[i][j] = A[j][i];
    }
  }
  
  //printmat(A); printmat(A_T); printmat(X);
  
  for(int test = 0; test < 10; test++){
    vector<LL> v;
    for(int i = 0; i < n; i++){
      v.push_back(rand() % 64);
    }
    vector<LL> Xv = matmul(X,v);
    vector<LL> AA_Tv = matmul(A, matmul(A_T,v));
    if(Xv != AA_Tv){
      cout << 0 << "\n";
      return;
    }
  }
  
  cout << 1 << "\n";
}

int main(){
  srand(345348345);
  LL t; cin >> t;
  while(t--) solve();
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: RUNTIME ERROR

Test 4

Verdict: RUNTIME ERROR

Test 5

Verdict: RUNTIME ERROR

Test 6

Verdict: RUNTIME ERROR

Test 7

Verdict: RUNTIME ERROR

Test 8

Verdict: RUNTIME ERROR

Test 9

Verdict: RUNTIME ERROR

Test 10

Verdict: RUNTIME ERROR