Problem p02361 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;

#define INF (INT_MAX / 2)
#define PI (2 * acos(0.0))
#define EPS (1e-8)

#define REP(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) REP(i, 0, n)

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

typedef int Cost;
struct Edge {
  int src, dst;
  Cost cst;
  Edge(int s, int d, Cost c) : src(s), dst(d), cst(c) {}
};
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;
typedef vector<Cost> Array;
typedef vector<Array> Matrix;

int dx[8] = {0, 1, 0, -1, 1, -1, 1, -1};
int dy[8] = {1, 0, -1, 0, 1, -1, -1, 1};

vector<Cost> dijkstra(const Graph &g, int s) {
  const Cost inf = numeric_limits<Cost>::max() / 2;
  typedef tuple<Cost, int> State;
  priority_queue<State> q;
  vector<Cost> dist(g.size(), inf);
  dist[s] = 0;
  q.emplace(0, s);
  while (q.size()) {
    Cost c;
    int v;
    tie(c, v) = q.top();
    q.pop();
    c *= -1;
    if (dist[v] < c)
      continue;
    for (auto &e : g[v]) {
      if (dist[e.dst] > dist[v] + e.cst) {
        dist[e.dst] = dist[v] + e.cst;
        q.emplace(dist[e.dst], e.dst);
      }
    }
  }
  return dist;
}

int main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int v, e, r;
  int s, t, d;

  cin >> v >> e >> r;

  Graph g(v);
  for (int i = 0; i < e; i++) {
    cin >> s >> t >> d;
    g[s].push_back(Edge(s, t, d));
  }

  vector<Cost> c = dijkstra(g, r);
  for (int i = 0; i < (int)c.size(); i++) {
    if (c[i] == numeric_limits<Cost>::max() / 2)
      cout << "INF" << endl;
    else
      cout << c[i] << endl;
  }
  return 0;
}

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

#define INF (INT_MAX / 2)
#define PI (2 * acos(0.0))
#define EPS (1e-8)

#define REP(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) REP(i, 0, n)

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

typedef int Cost;
struct Edge {
  int src, dst;
  Cost cst;
  Edge(int s, int d, Cost c) : src(s), dst(d), cst(c) {}
};
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;
typedef vector<Cost> Array;
typedef vector<Array> Matrix;

int dx[8] = {0, 1, 0, -1, 1, -1, 1, -1};
int dy[8] = {1, 0, -1, 0, 1, -1, -1, 1};

vector<Cost> dijkstra(const Graph &g, int s) {
  const Cost inf = numeric_limits<Cost>::max() / 2;
  typedef tuple<Cost, int> State;
  priority_queue<State, vector<State>, greater<State>> q;
  vector<Cost> dist(g.size(), inf);
  dist[s] = 0;
  q.emplace(0, s);
  while (q.size()) {
    Cost c;
    int v;
    tie(c, v) = q.top();
    q.pop();
    c *= -1;
    if (dist[v] < c)
      continue;
    for (auto &e : g[v]) {
      if (dist[e.dst] > dist[v] + e.cst) {
        dist[e.dst] = dist[v] + e.cst;
        q.emplace(dist[e.dst], e.dst);
      }
    }
  }
  return dist;
}

int main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int v, e, r;
  int s, t, d;

  cin >> v >> e >> r;

  Graph g(v);
  for (int i = 0; i < e; i++) {
    cin >> s >> t >> d;
    g[s].push_back(Edge(s, t, d));
  }

  vector<Cost> c = dijkstra(g, r);
  for (int i = 0; i < (int)c.size(); i++) {
    if (c[i] == numeric_limits<Cost>::max() / 2)
      cout << "INF" << endl;
    else
      cout << c[i] << endl;
  }
  return 0;
}