Problem p02678 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; --i)
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

using namespace std;
using ll = long long;
using ld = long double;
using pi = pair<ll, ll>;

int main() {
  ll n, m;
  cin >> n >> m;

  vector<vector<ll>> to(n);

  // ll to[n][n];
  //   cout<< "#"<<endl;

  vector<ll> v(n);
  vector<bool> visited(n, false);
  ll a, b;
  // cout<< "#"<<endl;
  rep(i, m) {
    cin >> a >> b;
    a--;
    b--;
    to[a].push_back(b);
    to[b].push_back(a);
  }
  queue<ll> q;
  q.push(0LL);
  v[0] = 0;
  while (!q.empty()) {
    ll cur = q.front();
    q.pop();
    for (auto x : to[cur]) {
      if (visited[x] == false) {
        v[x] = cur;
        visited[x] = true;
        q.push(x);
      }
    }
  }

  cout << "Yes" << endl;
  rep(i, n - 1) { cout << v[i + 1] + 1 << endl; }

  return 0;
}


Error: 0

Fixed submission:

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; --i)
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

using namespace std;
using ll = long long;
using ld = long double;
using pi = pair<ll, ll>;

// auto mod int
// https://youtu.be/L8grWxBlIZ4?t=9858
// https://youtu.be/ERZuLAxZffQ?t=4807 : optimize
// https://youtu.be/8uowVvQ_-Mo?t=1329 : division
const int mod = 998244353;
struct mint {
  ll x; // typedef long long ll;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint a) {
    if ((x += a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator-=(const mint a) {
    if ((x += mod - a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const { return mint(*this) += a; }
  mint operator-(const mint a) const { return mint(*this) -= a; }
  mint operator*(const mint a) const { return mint(*this) *= a; }
  mint pow(ll t) const {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod - 2); }
  mint &operator/=(const mint a) { return *this *= a.inv(); }
  mint operator/(const mint a) const { return mint(*this) /= a; }
};
istream &operator>>(istream &is, const mint &a) { return is >> a.x; }
ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }
// combination mod prime
// https://www.youtube.com/watch?v=8uowVvQ_-Mo&feature=youtu.be&t=1619
struct combination {
  vector<mint> fact, ifact;
  combination(int n) : fact(n + 1), ifact(n + 1) {
    assert(n < mod);
    fact[0] = 1;
    for (int i = 1; i <= n; ++i)
      fact[i] = fact[i - 1] * i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i)
      ifact[i - 1] = ifact[i] * i;
  }
  mint operator()(int n, int k) {
    if (k < 0 || k > n)
      return 0;
    return fact[n] * ifact[k] * ifact[n - k];
  }
} c(200005);

int main() {
  ll m, n;
  cin >> n >> m;

  ll to[n][n];
  rep(i, n) rep(j, n) to[i][j] = -1;
  vector<ll> v(n);
  vector<bool> visited(n, false);
  ll a, b;
  rep(i, m) {
    cin >> a >> b;
    a--;
    b--;
    to[a][b] = 1;
    to[b][a] = 1;
  }

  queue<ll> q;
  q.push(0LL);
  v[0] = 0;
  while (!q.empty()) {
    ll cur = q.front();
    q.pop();
    rep(i, n) {
      if (to[cur][i] > 0) {
        if (visited[i] == false) {
          v[i] = cur;
          visited[i] = true;
          q.push(i);
        }
      }
    }
  }

  cout << "Yes" << endl;
  rep(i, n - 1) { cout << v[i + 1] + 1 << endl; }

  return 0;
}