Problem p00346 (C++) — buggy submission, verdict: Time Limit Exceeded

/* {{{ Shinobu kawaii */
/*
  ______   __        _                  __
.' ____ \\ [  |      (_)                [  |
| (___ \\_| | |--.   __   _ .--.   .--.  | |.--.   __   _
 _.____`.  | .-. | [  | [ `.-. |/ .'`\\ \\| '/'`\\ \\[  | | |
| \\____) | | | | |  | |  | | | || \\__. ||  \\__/ | | \\_/ |,
 \\______.'[___]|__][___][___||__]'.__.'[__;.__.'  '.__.'_/

*/
// clang-format off
/* }}} */

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

// #define int long long
struct Fast {Fast(){std::cin.tie(0);ios::sync_with_stdio(false);}} fast;

/* cpp template {{{ */

/* short */
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second
#define ALL(v) begin(v), end(v)
#define RALL(v) rbegin(v), rend(v)
#define X real()
#define Y imag()

/* REPmacro */
#define REPS(i, a, n) for (ll i = (a); i < (ll)(n); ++i)
#define REP(i, n) REPS(i, 0, n)
#define RREP(i, n) REPS(i, 1, n + 1)
#define DEPS(i, a, n) for (ll i = (a); i >= (ll)(n); --i)
#define DEP(i, n) DEPS(i, n, 0)
#define EACH(i, n) for (auto&& i : n)

/* debug */
#define debug(x) cerr << x << " " << "(L:" << __LINE__ << ")" << '\\n';

/* alias */
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;
using D = double;
using P = complex<D>;
using vs = vector<string>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const int INF = 1001001001;
const ll LINF = 1001001001001001001ll;
const int MOD = 1e9 + 7;
const D EPS = 1e-9;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};

/* func */
inline bool inside(int y, int x, int H, int W) {return y >= 0 && x >= 0 && y < H && x < W;}
inline int in() {int x; cin >> x; return x;}
inline ll IN() {ll x; cin >> x; return x;}
inline vs split(const string& t, char c) {vs v; stringstream s(t); string b; while(getline(s, b, c)) v.eb(b); return v;}
template <typename T> inline bool chmin(T& a, const T& b) {if (a > b) a = b; return a > b;}
template <typename T> inline bool chmax(T& a, const T& b) {if (a < b) a = b; return a < b;}
template <typename T, typename S> inline void print(const pair<T, S>& p) {cout << p.first << " " << p.second << endl;}
template <typename T> inline void print(const T& x) {cout << x << '\\n';}
template <typename T, typename S> inline void print(const vector<pair<T, S>>& v) {for (auto&& p : v) print(p);}
template <typename T> inline void print(const vector<T>& v, string s = " ") {REP(i, v.size()) cout << v[i] << (i != (ll)v.size() - 1 ? s : "\\n");}
// clang-format on
/* }}} */

struct Edge {
  Edge() {}
  Edge(int a, int b) {
    to = a;
    cost = b;
  }
  int to, cost;
};
int N, R;
vector<Edge> G[1500];
vi Gprev[1500][1500];
map<int, bool> chie;

void dijkstra(int s, vi &d) {
  minPQ<pii> q;
  d[s] = 0;
  q.emplace(0, s);

  while (q.size()) {
    auto p = q.top();
    q.pop();
    int v = p.Se;
    if (d[v] < p.Fi)
      continue;
    EACH(e, G[v]) {
      if (d[e.to] == d[v] + e.cost) {
        Gprev[s][e.to].eb(v);
        q.emplace(d[e.to], e.to);
      } else if (d[e.to] > d[v] + e.cost) {
        d[e.to] = d[v] + e.cost;
        Gprev[s][e.to] = vi();
        Gprev[s][e.to].eb(v);
        q.emplace(d[e.to], e.to);
      }
    }
  }
}

void bfs(int s, int t) {
  queue<int> q;
  q.emplace(s);
  bool vis[1500] = {};
  while (q.size()) {
    int p = q.front();
    q.pop();
    if (vis[p])
      continue;
    chie[p] = true;
    vis[p] = true;
    EACH(e, Gprev[t][p]) { q.emplace(e); }
  }
}

signed main() {
  cin >> N >> R;
  vvi d(N, vi(N, INF));
  REP(i, R) {
    int s = in() - 1, t = in() - 1, d = in();
    G[s].eb(t, d);
    G[t].eb(s, d);
  }
  REP(i, N) dijkstra(i, d[i]);

  int ma = 0;
  REP(i, N) REP(j, N) chmax(ma, d[i][j]);

  REP(i, N) REP(j, N) {
    if (ma == d[i][j]) {
      bfs(j, i);
    }
  }

  print(N - chie.size());
  REP(i, N) {
    if (!chie[i])
      print(i + 1);
  }

  return 0;
}

Error: TLE

Fixed submission:

/* {{{ Shinobu kawaii */
/*
  ______   __        _                  __
.' ____ \\ [  |      (_)                [  |
| (___ \\_| | |--.   __   _ .--.   .--.  | |.--.   __   _
 _.____`.  | .-. | [  | [ `.-. |/ .'`\\ \\| '/'`\\ \\[  | | |
| \\____) | | | | |  | |  | | | || \\__. ||  \\__/ | | \\_/ |,
 \\______.'[___]|__][___][___||__]'.__.'[__;.__.'  '.__.'_/

*/
// clang-format off
/* }}} */

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

// #define int long long
struct Fast {Fast(){std::cin.tie(0);ios::sync_with_stdio(false);}} fast;

/* cpp template {{{ */

/* short */
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second
#define ALL(v) begin(v), end(v)
#define RALL(v) rbegin(v), rend(v)
#define X real()
#define Y imag()

/* REPmacro */
#define REPS(i, a, n) for (ll i = (a); i < (ll)(n); ++i)
#define REP(i, n) REPS(i, 0, n)
#define RREP(i, n) REPS(i, 1, n + 1)
#define DEPS(i, a, n) for (ll i = (a); i >= (ll)(n); --i)
#define DEP(i, n) DEPS(i, n, 0)
#define EACH(i, n) for (auto&& i : n)

/* debug */
#define debug(x) cerr << x << " " << "(L:" << __LINE__ << ")" << '\\n';

/* alias */
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;
using D = double;
using P = complex<D>;
using vs = vector<string>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const int INF = 1001001001;
const ll LINF = 1001001001001001001ll;
const int MOD = 1e9 + 7;
const D EPS = 1e-9;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};

/* func */
inline bool inside(int y, int x, int H, int W) {return y >= 0 && x >= 0 && y < H && x < W;}
inline int in() {int x; cin >> x; return x;}
inline ll IN() {ll x; cin >> x; return x;}
inline vs split(const string& t, char c) {vs v; stringstream s(t); string b; while(getline(s, b, c)) v.eb(b); return v;}
template <typename T> inline bool chmin(T& a, const T& b) {if (a > b) a = b; return a > b;}
template <typename T> inline bool chmax(T& a, const T& b) {if (a < b) a = b; return a < b;}
template <typename T, typename S> inline void print(const pair<T, S>& p) {cout << p.first << " " << p.second << endl;}
template <typename T> inline void print(const T& x) {cout << x << '\\n';}
template <typename T, typename S> inline void print(const vector<pair<T, S>>& v) {for (auto&& p : v) print(p);}
template <typename T> inline void print(const vector<T>& v, string s = " ") {REP(i, v.size()) cout << v[i] << (i != (ll)v.size() - 1 ? s : "\\n");}
// clang-format on
/* }}} */

struct Edge {
  Edge() {}
  Edge(int a, int b) {
    to = a;
    cost = b;
  }
  int to, cost;
};
int N, R;
vector<Edge> G[1500];
bool res[1500];
int cnt;

void dijkstra(int s, vi &d) {
  minPQ<pii> q;
  d[s] = 0;
  q.emplace(0, s);

  while (q.size()) {
    auto p = q.top();
    q.pop();
    int v = p.Se;
    if (d[v] < p.Fi)
      continue;
    EACH(e, G[v]) {
      if (d[e.to] > d[v] + e.cost) {
        d[e.to] = d[v] + e.cost;
        q.emplace(d[e.to], e.to);
      }
    }
  }
}

void bfs(int s, vi &d) {
  queue<pii> q;
  q.emplace(s, d[s]);
  bool vis[1500] = {};
  while (q.size()) {
    auto p = q.front();
    q.pop();
    if (vis[p.Fi])
      continue;
    if (!res[p.Fi])
      cnt++;
    res[p.Fi] = true;
    vis[p.Fi] = true;
    EACH(e, G[p.Fi]) {
      if (d[e.to] != d[p.Fi] - e.cost)
        continue;
      q.emplace(e.to, d[e.to]);
    }
  }
}

signed main() {
  cin >> N >> R;
  vvi d(N, vi(N, INF));
  REP(i, R) {
    int s = in() - 1, t = in() - 1, d = in();
    G[s].eb(t, d);
    G[t].eb(s, d);
  }
  REP(i, N) dijkstra(i, d[i]);

  int ma = 0;
  REP(i, N) REP(j, N) chmax(ma, d[i][j]);

  REP(i, N) REP(j, N) {
    if (ma == d[i][j]) {
      bfs(j, d[i]);
    }
  }
  print(N - cnt);
  REP(i, N) {
    if (!res[i])
      print(i + 1);
  }

  return 0;
}