Ruudukko

input/code.cpp: In function 'std::__cxx11::string etsi(ll, ll)':
input/code.cpp:31:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < a.size(); ++i) {
                     ~~^~~~~~~~~~
input/code.cpp:41:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if (s.size() == p) s += a;
         ~~~~~~~~~^~~~

#include <iostream>
#include <vector>
#include<algorithm>
#include <set>
#include <map>
using namespace std;
using ll = long long;
char t[501][501];
string ta[501][501];
ll n;

string etsi(ll x, ll y) {
  string s = "";
  if (ta[x][y] != "") return ta[x][y];
  //cout << x << " " << y << " " << s << endl;
  if (x == y && x == n-1) return "";
  if (x+1 >= n || (y+1 < n && t[x+1][y] > t[x][y+1])) {
    s += t[x][y+1];
    //if (x == 2) cout << s << " testi" << endl;
    s += etsi(x, y+1);
  }
  else if (y+1 >= n || (x+1 < n && t[x+1][y] < t[x][y+1])) {
    s += t[x+1][y];
    s+= etsi(x+1, y);
  }
  else if (y+1 < n && x+1 < n) {
    s += t[x+1][y];
    string a = etsi(x+1, y);
    string b = etsi(x, y+1);
    ll p = s.size();
    for (int i = 0; i < a.size(); ++i) {
      if (a[i] > b[i]) {
        s += b;
        break;
      }
      else if (a[i] < b[i]) {
        s += a;
        break;
      }
    }
    if (s.size() == p) s += a;
  }
  //cout << x << " " << y << " " << s << endl;
  ta[x][y] = s;
  return s;
}

int main() {
  char a;
  cin >> n;
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < n; ++j) {
      cin >> a;
      t[i][j] = a;
    }
  }
  //cout << "lol" << endl;
  string s = "";
  s += t[0][0];
  s += etsi(0,0);
  cout << s << endl;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: RUNTIME ERROR

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED