Problem p02678 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> l_l;
typedef pair<int, int> i_i;
typedef vector<ll> vl;
typedef vector<int> vi;
typedef vector<char> vec;
typedef vector<bool> veb;
typedef vector<string> ves;
typedef vector<vector<ll>> vvl;
typedef vector<vector<int>> vvi;
typedef vector<vector<char>> vvec;
typedef vector<vector<bool>> vveb;
typedef vector<vector<string>> vves;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i < (int)(n); i++)
#define rep2(i, n) for (int i = 2; i < (int)(n); i++)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define fs first
#define sc second
#define pb push_back
#define pp pop_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define maxel(a) *max_element(all(a))
#define minel(a) *min_element(all(a))
#define acc accumulate
#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))
#define mod (1000000007)
typedef long long int64;
// const int64 INF = 1LL << 58;
#define dame                                                                   \\
  {                                                                            \\
    puts("-1");                                                                \\
    return 0;                                                                  \\
  }
#define YES                                                                    \\
  {                                                                            \\
    cout << "YES" << endl;                                                     \\
    return 0;                                                                  \\
  }
#define NO                                                                     \\
  {                                                                            \\
    cout << "NO" << endl;                                                      \\
    return 0;                                                                  \\
  }
#define Yes                                                                    \\
  {                                                                            \\
    cout << "Yes" << endl;                                                     \\
    return 0;                                                                  \\
  }
#define No                                                                     \\
  {                                                                            \\
    cout << "No" << endl;                                                      \\
    return 0;                                                                  \\
  }
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;
}
int dx[] = {0, 0, -1, 1};
int dy[] = {1, -1, 0, 0};
int N = 10001;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n, m;
  cin >> n >> m;
  vvi g(n);
  rep(i, m) {
    int a, b;
    cin >> a >> b;
    --a;
    --b;
    g[a].pb(b);
    g[b].pb(a);
  }
  /*
  rep1(i,n){
      for(auto it : g[i]) cout <<  it + 1 << " ";
      cout  << endl;
  }
  */
  vi dist(n, INF);
  vi before(n, INF);
  queue<int> q;

  auto push = [&](int v, int d, int b) {
    if (dist[v] != INF)
      return;
    dist[v] = d;
    before[v] = b;
    q.push(v);
  };
  push(0, 0, 0);
  while (!q.empty()) {
    int v = q.front();
    q.pop();
    int d = dist[v];
    rep(i, g[v].size()) { push(g[v][i], d + 1, v); }
  }

  rep(i, n) {
    if (dist[i] == INF)
      No
  }
  cout << "Yes" << endl;
  rep1(i, n) { cout << before[i] + 1 << endl; }
  return 0;
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> l_l;
typedef pair<int, int> i_i;
typedef vector<ll> vl;
typedef vector<int> vi;
typedef vector<char> vec;
typedef vector<bool> veb;
typedef vector<string> ves;
typedef vector<vector<ll>> vvl;
typedef vector<vector<int>> vvi;
typedef vector<vector<char>> vvec;
typedef vector<vector<bool>> vveb;
typedef vector<vector<string>> vves;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i < (int)(n); i++)
#define rep2(i, n) for (int i = 2; i < (int)(n); i++)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define fs first
#define sc second
#define pb push_back
#define pp pop_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define maxel(a) *max_element(all(a))
#define minel(a) *min_element(all(a))
#define acc accumulate
#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))
#define mod (1000000007)
typedef long long int64;
// const int64 INF = 1LL << 58;
#define dame                                                                   \\
  {                                                                            \\
    puts("-1");                                                                \\
    return 0;                                                                  \\
  }
#define YES                                                                    \\
  {                                                                            \\
    cout << "YES" << endl;                                                     \\
    return 0;                                                                  \\
  }
#define NO                                                                     \\
  {                                                                            \\
    cout << "NO" << endl;                                                      \\
    return 0;                                                                  \\
  }
#define Yes                                                                    \\
  {                                                                            \\
    cout << "Yes" << endl;                                                     \\
    return 0;                                                                  \\
  }
#define No                                                                     \\
  {                                                                            \\
    cout << "No" << endl;                                                      \\
    return 0;                                                                  \\
  }
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;
}
int dx[] = {0, 0, -1, 1};
int dy[] = {1, -1, 0, 0};
int N = 10001;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n, m;
  cin >> n >> m;
  vvi g(n);
  rep(i, m) {
    int a, b;
    cin >> a >> b;
    --a;
    --b;
    g[a].pb(b);
    g[b].pb(a);
  }
  /*
  rep1(i,n){
      for(auto it : g[i]) cout <<  it + 1 << " ";
      cout  << endl;
  }
  */
  vi dist(n, INF);
  queue<int> q;

  auto push = [&](int v, int d) {
    if (dist[v] != INF)
      return;
    dist[v] = d;
    q.push(v);
  };
  push(0, 0);
  while (!q.empty()) {
    int v = q.front();
    q.pop();
    int d = dist[v];
    rep(i, g[v].size()) { push(g[v][i], d + 1); }
  }

  rep(i, n) {
    if (dist[i] == INF)
      No
  }
  cout << "Yes" << endl;
  // for(auto it : g[1]) cout << it << endl;
  vvi ans(n);
  rep1(i, n) { ans[dist[i]].pb(i); }
  /*
  rep1(i,n){
      for(auto it : ans[i]) cout <<  it + 1 << " ";
      cout  <<  endl;
  }
  */

  rep1(i, n) {
    int tmp = dist[i]; // 現在の深さ
    bool flg = false;
    if (dist[i] == 1) {
      cout << 1 << endl;
      continue;
    }
    rep(j, ans[tmp - 1].size()) {
      rep(k, g[i].size()) {
        if (ans[tmp - 1][j] == g[i][k]) {
          cout << ans[tmp - 1][j] + 1 << endl;
          flg = true;
          break;
        }
      }
      if (flg) {
        break;
      }
    }
  }
  return 0;
}