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

/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author
 */

// Created by White Knife on 15/04/20.
// doot diddly donger cuckerino Hahahahahah

#pragma GCC optimize("O3")
#pragma GCC target("sse4")
#pragma GCC target("popcnt")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace __gnu_cxx;
using namespace std;

// @formatter:off
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
#define sz(x) (long long)(x).size()
#define sim template <typename T
#define ris return *this
#define dor > debug &operator<<
#define eni(x)                                                                 \\
  sim > typename enable_if<sizeof dud<T>(0) x 1, debug &>::type operator<<(T i)
sim > struct rge {
  T b, e;
};
sim > rge<T> rang(T i, T j) { return rge<T>{i, j}; }
sim > auto dud(T *x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
  ~debug() { cerr << endl; }
  eni(!=) {
    cerr << boolalpha << i;
    ris;
  }
  eni(==) { ris << rang(all(i)); }
  sim, typename U dor(pair<U, T> d) {
    ris << "(" << d.first << ", " << d.second << ")";
  }
  sim dor(rge<T> d) {
    *this << "[";
    for (auto it = d.b; it != d.e; ++it)
      *this << ", " + 2 * (it == d.b) << *it;
    ris << "]";
  }
#else
  sim dor(const T &) { ris; }
#endif
};
#define pr(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "

using ll = long long;
using ull = unsigned long long;
using ld = long double;
// using li = __int128;
// using uli = unsigned __int128;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vb = vector<bool>;

using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vpii = vector<pii>;
using vpll = vector<pll>;
template <typename T>
using ordered_set =
    tree<T, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update>;

const ld PI = acos(-1);

template <typename T> inline T mini(T &x, T y) { return x = min(x, y); }
template <typename T> inline T maxi(T &x, T y) { return x = max(x, y); }
template <typename T> T rand(T x, T y) { return rand() % (y - x + 1) + x; }
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
// @formatter:on

struct DSU {
  int n;
  std::vector<int> par;
  std::vector<long long> rank;

  explicit DSU(int _n) : n(_n) {
    par.resize(n);
    rank.resize(n);
    for (int i = 0; i < n; ++i) {
      par[i] = i;
      rank[i] = 1;
    }
  }
  explicit DSU(std::vector<long long> &_rank) : rank(move(_rank)) {
    n = rank.size();
    par.resize(n);
    iota(par.begin(), par.end(), 0);
  }

  int Root(int x) { return x == par[x] ? x : par[x] = Root(par[x]); }

  bool Unite(int x, int y) {
    x = Root(x);
    y = Root(y);
    if (x == y)
      return true;
    if (rank[x] > rank[y]) {
      par[y] = x;
      rank[x] += rank[y];
    } else if (rank[y] > rank[x]) {
      par[x] = y;
      rank[y] += rank[x];
    } else {
      par[x] = y;
      rank[y]++;
    }
    return false;
  }

  int Count() {
    int cnt = 0;
    for (int i = 0; i < n; ++i) {
      if (Root(i) == i)
        cnt++;
    }
    return cnt;
  }
};

class DDoubleDots {
public:
  int n, m;
  vector<vector<int>> g;
  vector<bool> vis;
  //  vector<int> dist;
  vector<int> nex;

  vector<ll> dijkstra(int src) {
    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<>> pq;
    vector<ll> dist(n, 1e9 + 7);
    pq.push(make_pair(0, src));
    dist[src] = 0;
    while (!pq.empty()) {
      int u = pq.top().second;
      pq.pop();
      for (int v : g[u]) {
        int weight = 1;
        if (dist[v] > dist[u] + weight) {
          dist[v] = dist[u] + weight;
          nex[v] = u;
          pq.push({dist[v], v});
        }
      }
    }
    return dist;
  }

  void solve(std::istream &cin, std::ostream &cout) {
    cin >> n >> m;
    vis.resize(n, false);
    nex.resize(n, -1);
    //    dist.resize(n, 0);
    g = vector<vector<int>>(n);
    for (int i = 0; i < m; ++i) {
      int x, y;
      cin >> x >> y;
      g[x - 1].push_back(y - 1);
      g[y - 1].push_back(x - 1);
    }
    nex[0] = 0;
    //    queue<int> q;
    //    q.push(0);
    //    while (!q.empty()) {
    //      int v = q.front();
    //      vis[v] = 1;
    //      q.pop();
    //      for (int u: g[v]) {
    //        if (vis[u] || u == 0) continue;
    //        if (nex[u] == -1) nex[u] = v;
    //        q.push(u);
    //      }
    //    }
    dijkstra(0);
    bool ok = 1;
    for (int i = 1; i < n; ++i) {
      if (nex[i] == -1)
        ok = false;
    }
    cout << (ok ? "Yes" : "No") << '\\n';
    //    if (!ok) return;
    for (int i = 1; i < n; ++i) {
      cout << nex[i] + 1 << "\\n";
    }
  }
};

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  std::cout.tie(nullptr);
  DDoubleDots solver;
  std::istream &in(std::cin);
  std::ostream &out(std::cout);
  solver.solve(in, out);
  return 0;
}


Error: TLE

Fixed submission:

/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author
 */

// Created by White Knife on 15/04/20.
// doot diddly donger cuckerino Hahahahahah

#pragma GCC optimize("O3")
#pragma GCC target("sse4")
#pragma GCC target("popcnt")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace __gnu_cxx;
using namespace std;

// @formatter:off
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
#define sz(x) (long long)(x).size()
#define sim template <typename T
#define ris return *this
#define dor > debug &operator<<
#define eni(x)                                                                 \\
  sim > typename enable_if<sizeof dud<T>(0) x 1, debug &>::type operator<<(T i)
sim > struct rge {
  T b, e;
};
sim > rge<T> rang(T i, T j) { return rge<T>{i, j}; }
sim > auto dud(T *x) -> decltype(cerr << *x, 0);
sim > char dud(...);
struct debug {
#ifdef LOCAL
  ~debug() { cerr << endl; }
  eni(!=) {
    cerr << boolalpha << i;
    ris;
  }
  eni(==) { ris << rang(all(i)); }
  sim, typename U dor(pair<U, T> d) {
    ris << "(" << d.first << ", " << d.second << ")";
  }
  sim dor(rge<T> d) {
    *this << "[";
    for (auto it = d.b; it != d.e; ++it)
      *this << ", " + 2 * (it == d.b) << *it;
    ris << "]";
  }
#else
  sim dor(const T &) { ris; }
#endif
};
#define pr(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "

using ll = long long;
using ull = unsigned long long;
using ld = long double;
// using li = __int128;
// using uli = unsigned __int128;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vb = vector<bool>;

using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vpii = vector<pii>;
using vpll = vector<pll>;
template <typename T>
using ordered_set =
    tree<T, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update>;

const ld PI = acos(-1);

template <typename T> inline T mini(T &x, T y) { return x = min(x, y); }
template <typename T> inline T maxi(T &x, T y) { return x = max(x, y); }
template <typename T> T rand(T x, T y) { return rand() % (y - x + 1) + x; }
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());
// @formatter:on

struct DSU {
  int n;
  std::vector<int> par;
  std::vector<long long> rank;

  explicit DSU(int _n) : n(_n) {
    par.resize(n);
    rank.resize(n);
    for (int i = 0; i < n; ++i) {
      par[i] = i;
      rank[i] = 1;
    }
  }
  explicit DSU(std::vector<long long> &_rank) : rank(move(_rank)) {
    n = rank.size();
    par.resize(n);
    iota(par.begin(), par.end(), 0);
  }

  int Root(int x) { return x == par[x] ? x : par[x] = Root(par[x]); }

  bool Unite(int x, int y) {
    x = Root(x);
    y = Root(y);
    if (x == y)
      return true;
    if (rank[x] > rank[y]) {
      par[y] = x;
      rank[x] += rank[y];
    } else if (rank[y] > rank[x]) {
      par[x] = y;
      rank[y] += rank[x];
    } else {
      par[x] = y;
      rank[y]++;
    }
    return false;
  }

  int Count() {
    int cnt = 0;
    for (int i = 0; i < n; ++i) {
      if (Root(i) == i)
        cnt++;
    }
    return cnt;
  }
};

class DDoubleDots {
public:
  vector<vector<int>> g;
  vector<bool> vis;
  vector<int> nex;

  void solve(std::istream &cin, std::ostream &cout) {
    int n, m;
    cin >> n >> m;
    vis.resize(n, false);
    nex.resize(n, -1);
    g = vector<vector<int>>(n);
    for (int i = 0; i < m; ++i) {
      int x, y;
      cin >> x >> y;
      g[x - 1].push_back(y - 1);
      g[y - 1].push_back(x - 1);
    }
    nex[0] = 0;
    queue<int> q;
    q.push(0);
    while (!q.empty()) {
      int v = q.front();
      vis[v] = 1;
      q.pop();
      for (int u : g[v]) {
        if (vis[u] || u == 0)
          continue;
        if (nex[u] == -1)
          nex[u] = v;
        q.push(u);
      }
    }
    bool ok = 1;
    for (int i = 1; i < n; ++i) {
      if (nex[i] == -1)
        ok = false;
    }
    cout << (ok ? "Yes" : "No") << '\\n';
    if (!ok)
      return;
    for (int i = 1; i < n; ++i) {
      cout << nex[i] + 1 << "\\n";
    }
  }
};

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  std::cout.tie(nullptr);
  DDoubleDots solver;
  std::istream &in(std::cin);
  std::ostream &out(std::cout);
  solver.solve(in, out);
  return 0;
}