Ruudukko

#include <bits/stdc++.h>

#define ll long long
using namespace std;

int n;
vector<string> ans;
string str[500][500];

void bt(int y, int x, string now){
    now=now+str[y][x];
    if(x==n-1&&y==n-1){
        ans.push_back(now);
        return;
    }
    else if(x==n-1)bt(y+1, x, now);
    else if(y==n-1)bt(y, x+1, now);
    else if(str[y][x+1]==str[y+1][x]){
        bt(y+1, x, now); bt(y, x+1, now);
        return;
    }
    else if(str[y][x+1]<str[y+1][x]){
        bt(y, x+1, now);
    }
    else bt(y+1, x, now);

}

int main()
{
    cin >> n;
    for(int i = 0; i < n; ++i){
        for(int k = 0; k < n; ++k){
            char c; cin >> c;
            str[i][k].push_back(c);
        }
    }
    bt(0, 0, "");
    string s = ans[0];
    for(auto c : ans){
        if(s>c)s=c;
    }
    cout << s;





    return 0;
}

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: TIME LIMIT EXCEEDED

Test 7

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 3

Verdict: RUNTIME ERROR

Test 15

Group: 3

Verdict: TIME LIMIT EXCEEDED