Snakeless path

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

template <typename T>
std::ostream &operator<<(std::ostream &os, const std::vector<T> &v) {
  os << "[";
  for (int i = 0; i < v.size(); ++i) {
    os << v[i];
    if (i != v.size() - 1)
      os << ", ";
  }
  os << "]";
  return os;
}

ll bfs(std::unordered_set<ll> &snakePos, ll start, ll end, ll landMarkCount,
       std::vector<ll> &path) {
  std::queue<ll> qq;
  std::vector<char> checked(landMarkCount * landMarkCount, 0);
  qq.push(start);
  checked[start] = 1;
  while (!qq.empty()) {
    ll cur = qq.front();
    qq.pop();

    // std::cout << "MOII " << cur << std::endl;
    for (ll ii = 0; ii < landMarkCount; ii++) {
      ll next1 = cur * landMarkCount + ii;
      // ll next2 = ii * landMarkCount + cur;
      if (!checked[next1] && !snakePos.contains(next1) && ii != cur) {
        qq.push(ii);
        checked[next1] = 1;
        path[ii] = cur;
        if (ii == end) {
          // path[next] = ii;
          return 1;
        }
      }
    }
  }
  // return checked[end];
  return 0;
}

int main() {
  ll landMarkCount, snakeCount;
  std::cin >> landMarkCount;
  std::cin >> snakeCount;

  std::unordered_set<ll> snakePos;
  for (ll ii = 0; ii < snakeCount; ii++) {
    ll start, end;
    // std::cout << start << " " << end << " " << speed << std::endl;
    std::cin >> start;
    std::cin >> end;

    snakePos.insert((end - 1) * landMarkCount + (start - 1));
    snakePos.insert((start - 1) * landMarkCount + (end - 1));
  }

  ll start = 0;
  ll end = landMarkCount - 1;

  std::vector<ll> path(landMarkCount, -1);
  ll success = bfs(snakePos, start, end, landMarkCount, path);
  if (!success) {
    std::cout << "0" << std::endl;
    return 0;
  }

  ll ss = end;
  // std::cout << path << std::endl;
  // return 0;
  std::vector<ll> retPath;
  while (ss != start) {
    // minSpeed = std::min(minSpeed, teleportMap[path[ss]][ss]);
    retPath.push_back(ss);
    ss = path[ss];
  }
  std::cout << retPath.size() + 1 << std::endl;
  std::cout << 1 << " ";
  for (ll ii = retPath.size() - 1; ii > 0; ii--) {
    std::cout << retPath[ii] + 1 << " ";
  }
  std::cout << retPath[0] + 1 << std::endl;

  // ll vv = end;
  // while (vv != start) {
  //   ll uu = path[vv];
  //   teleportMap[uu][vv] -= minSpeed;
  //   teleportMap[vv][uu] += minSpeed;
  //   vv = uu;
  // }
  // std::cout << throughtPut << std::endl;
}

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: RUNTIME ERROR

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: RUNTIME ERROR

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: RUNTIME ERROR

Test 21

Verdict: RUNTIME ERROR

Test 22

Verdict: RUNTIME ERROR

Test 23

Verdict: RUNTIME ERROR

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: RUNTIME ERROR

Test 31

Verdict: RUNTIME ERROR

Test 32

Verdict: RUNTIME ERROR

Test 33

Verdict: RUNTIME ERROR

Test 34

Verdict: ACCEPTED

Test 35

Verdict: ACCEPTED

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: ACCEPTED

Test 39

Verdict: ACCEPTED

Test 40

Verdict: RUNTIME ERROR

Test 41

Verdict: RUNTIME ERROR

Test 42

Verdict: RUNTIME ERROR

Test 43

Verdict: RUNTIME ERROR

Test 44

Verdict: ACCEPTED

Test 45

Verdict: ACCEPTED

Test 46

Verdict: ACCEPTED

Test 47

Verdict: ACCEPTED

Test 48

Verdict: ACCEPTED

Test 49

Verdict: ACCEPTED

Test 50

Verdict: RUNTIME ERROR

Test 51

Verdict: RUNTIME ERROR

Test 52

Verdict: RUNTIME ERROR

Test 53

Verdict: RUNTIME ERROR

Test 54

Verdict: ACCEPTED

Test 55

Verdict: ACCEPTED

Test 56

Verdict: ACCEPTED

Test 57

Verdict: ACCEPTED

Test 58

Verdict: ACCEPTED

Test 59

Verdict: ACCEPTED

Test 60

Verdict: ACCEPTED

Test 61

Verdict: TIME LIMIT EXCEEDED

Test 62

Verdict: TIME LIMIT EXCEEDED

Test 63

Verdict: ACCEPTED

Test 64

Verdict: RUNTIME ERROR

Test 65

Verdict: ACCEPTED

Test 66

Verdict: ACCEPTED

Test 67

Verdict: ACCEPTED

Test 68

Verdict: ACCEPTED

Test 69

Verdict: ACCEPTED

Test 70

Verdict: RUNTIME ERROR

Test 71

Verdict: RUNTIME ERROR

Test 72

Verdict: RUNTIME ERROR

Test 73

Verdict: RUNTIME ERROR

Test 74

Verdict: RUNTIME ERROR

Test 75

Verdict: RUNTIME ERROR

Test 76

Verdict: RUNTIME ERROR

Test 77

Verdict: RUNTIME ERROR

Test 78

Verdict: RUNTIME ERROR

Test 79

Verdict: RUNTIME ERROR

Test 80

Verdict: RUNTIME ERROR

Test 81

Verdict: RUNTIME ERROR

Test 82

Verdict: RUNTIME ERROR

Test 83

Verdict: RUNTIME ERROR

Test 84

Verdict: RUNTIME ERROR

Test 85

Verdict: RUNTIME ERROR

Test 86

Verdict: RUNTIME ERROR

Test 87

Verdict: RUNTIME ERROR

Test 88

Verdict: RUNTIME ERROR

Test 89

Verdict: RUNTIME ERROR