King of the Waves

#include <bits/stdc++.h>
#define ll unsigned long long

typedef long double ld;

using namespace std;

vector<int> v[1001];
int res[1001];
int resi;
bool visited[1001];

int dfs(int i) {
  if(visited[i]) return 0;
  visited[i] = true;
  int r = 1;
  for(auto neigh : v[i]) {
    r += dfs(neigh);
  }
  res[resi++]=i;
  return r;
}

int main() {
  int n;
  cin >> n;
  for(int i=0;i<n;i++) {
    for(int j=0;j<n;j++) {
      char c;
      cin >> c;
      if(c == '1') {
        v[i].push_back(j);
      }
    }
  }
  int count = dfs(0);
  if(count == n) {
    for(int i=0;i<n;i++) {
      cout << res[i];
      if(i != n-1) {
        cout << " ";
      }
    } cout << endl;
  } else {
    cout << "impossible" << endl;
  }
  return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED