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

#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define vecll vector<long long>
#define vec2ll vector<vector<long long>>
#define vecpairll vector<pair<long long, long long>>
#define forll(s, a, b) for (long long s = a; s < b; s++)
#define forllde(s, a) for (long long s = a; s > 0; s--)

template <typename A, typename B> string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string &s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#define debug(...) cerr << "<" << #__VA_ARGS__ << ">:", debug_out(__VA_ARGS__)
#define INF LLONG_MAX

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

  map<ll, vecll> mym;
  vecll ans(n, 0);

  forll(i, 0, m) {
    cin >> a >> b;
    mym[a].push_back(b);
    mym[b].push_back(a);
  }

  queue<ll> s;
  s.push(1);
  while (not s.empty()) {
    ll next = s.front();
    s.pop();
    forll(i, 0, (ll)mym[next].size()) {
      if (ans[mym[next][i] - 1] == 0) {
        ans[mym[next][i] - 1] = next;
        s.push(mym[next][i]);
      }
    }
  }
  cout << "Yes" << endl;
  forll(i, 1, n) { cout << ans[i] << endl; }
}


Error: 0

Fixed submission:

#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define vecll vector<long long>
#define vec2ll vector<vector<long long>>
#define vecpairll vector<pair<long long, long long>>
#define forll(s, a, b) for (long long s = a; s < b; s++)
#define forllde(s, a) for (long long s = a; s > 0; s--)

template <typename A, typename B> string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string &s) { return '"' + s + '"'; }

string to_string(const char *s) { return to_string((string)s); }

string to_string(bool b) { return (b ? "true" : "false"); }

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N> string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A> string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B> string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " +
         to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail> void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#define debug(...) cerr << "<" << #__VA_ARGS__ << ">:", debug_out(__VA_ARGS__)
#define INF LLONG_MAX

int main() {
  ll n, m, c, a, b;
  cin >> n >> m;
  c = m;
  map<ll, vecll> mym;
  vecll ans(m, 0);

  forll(i, 0, m) {
    cin >> a >> b;
    mym[a].push_back(b);
    mym[b].push_back(a);
  }

  queue<ll> s;
  forll(i, 0, (ll)mym[1].size()) {
    if (ans[mym[1][i] - 1] == 0) {
      ans[mym[1][i] - 1] = 1;
      c--;
      s.push(mym[1][i]);
    }
  }
  while (not s.empty()) {
    if (c == 1)
      break;
    ll next = s.front();
    s.pop();
    forll(i, 0, (ll)mym[next].size()) {
      if (ans[mym[next][i] - 1] == 0) {
        ans[mym[next][i] - 1] = next;
        c--;
        s.push(mym[next][i]);
      }
    }
  }
  cout << "Yes" << endl;
  forll(i, 1, n) { cout << ans[i] << endl; }
}