Problem p03634 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <fstream>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;

#define REP(i, m, n) for (int i = (m); i < (int)(n); i++)
#define RREP(i, m, n) for (int i = (int)(n - 1); i >= m; i--)
#define rep(i, n) REP(i, 0, n)
#define rrep(i, n) RREP(i, 0, n)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define aut(r, v) __typeof(v) r = (v)
#define each(it, o) for (aut(it, (o).begin()); it != (o).end(); ++it)
#define reach(it, o) for (aut(it, (o).rbegin()); it != (o).rend(); ++it)
#define fi first
#define se second
#define debug(...)                                                             \
  {                                                                            \
    cerr << "[L" << __LINE__ << "] ";                                          \
    _debug(__VA_ARGS__);                                                       \
  }

template <typename T1, typename T2>
ostream &operator<<(ostream &o, const pair<T1, T2> &p) {
  return o << "(" << p.first << ", " << p.second << ")";
}
template <typename T> string join(const vector<T> &v, string del = ", ") {
  stringstream s;
  rep(i, v.size()) s << del << v[i];
  return s.str().substr(del.size());
}
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) {
  if (v.size())
    o << "[" << join(v) << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const vector<vector<T>> &vv) {
  int l = vv.size();
  if (l) {
    o << endl;
    rep(i, l) {
      o << (i == 0 ? "[ " : ",\n  ") << vv[i] << (i == l - 1 ? " ]" : "");
    }
  }
  return o;
}
template <typename T> ostream &operator<<(ostream &o, const set<T> &st) {
  vector<T> v(st.begin(), st.end());
  o << "{ " << join(v) << " }";
  return o;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &o, const map<T1, T2> &m) {
  each(p, m) {
    o << (p == m.begin() ? "{ " : ",\n  ") << *p
      << (p == --m.end() ? " }" : "");
  }
  return o;
}
inline void _debug() { cerr << endl; }
template <class First, class... Rest>
void _debug(const First &first, const Rest &...rest) {
  cerr << first << " ";
  _debug(rest...);
}

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;

const double PI = (1 * acos(0.0));
const double EPS = 1e-9;
const double mod = 1e9 + 7;
const ll INF = 0x3f3f3f3f;
const ll INFL = 0x3f3f3f3f3f3f3f3fLL;

inline void finput(string filename) { freopen(filename.c_str(), "r", stdin); }

struct edge {
  int to;
  ll cost;
};

int N, Q, K;
vector<edge> g[100010];
ll d[100010];

void dijk(int s) {
  priority_queue<int> pq;
  pq.push(s);
  d[s] = 0;

  while (!pq.empty()) {
    int u = pq.top();
    pq.pop();
    for (edge v : g[u]) {
      if (d[v.to] > d[u] + v.cost) {
        d[v.to] = d[u] + v.cost;
        pq.push(v.to);
      }
    }
  }
}

int main() {
  ios_base::sync_with_stdio(0);
  finput("./input");

  cin >> N;
  rep(i, N - 1) {
    int a, b;
    ll c;
    cin >> a >> b >> c;
    g[a].push_back({b, c});
    g[b].push_back({a, c});
  }

  cin >> Q >> K;
  fill(d, d + N + 1, INFL);
  dijk(K);

  rep(i, Q) {
    int x, y;
    cin >> x >> y;
    cout << d[x] + d[y] << endl;
  }

  return 0;
}


Fixed submission:
#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <fstream>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;

#define REP(i, m, n) for (int i = (m); i < (int)(n); i++)
#define RREP(i, m, n) for (int i = (int)(n - 1); i >= m; i--)
#define rep(i, n) REP(i, 0, n)
#define rrep(i, n) RREP(i, 0, n)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define aut(r, v) __typeof(v) r = (v)
#define each(it, o) for (aut(it, (o).begin()); it != (o).end(); ++it)
#define reach(it, o) for (aut(it, (o).rbegin()); it != (o).rend(); ++it)
#define fi first
#define se second
#define debug(...)                                                             \
  {                                                                            \
    cerr << "[L" << __LINE__ << "] ";                                          \
    _debug(__VA_ARGS__);                                                       \
  }

template <typename T1, typename T2>
ostream &operator<<(ostream &o, const pair<T1, T2> &p) {
  return o << "(" << p.first << ", " << p.second << ")";
}
template <typename T> string join(const vector<T> &v, string del = ", ") {
  stringstream s;
  rep(i, v.size()) s << del << v[i];
  return s.str().substr(del.size());
}
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) {
  if (v.size())
    o << "[" << join(v) << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const vector<vector<T>> &vv) {
  int l = vv.size();
  if (l) {
    o << endl;
    rep(i, l) {
      o << (i == 0 ? "[ " : ",\n  ") << vv[i] << (i == l - 1 ? " ]" : "");
    }
  }
  return o;
}
template <typename T> ostream &operator<<(ostream &o, const set<T> &st) {
  vector<T> v(st.begin(), st.end());
  o << "{ " << join(v) << " }";
  return o;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &o, const map<T1, T2> &m) {
  each(p, m) {
    o << (p == m.begin() ? "{ " : ",\n  ") << *p
      << (p == --m.end() ? " }" : "");
  }
  return o;
}
inline void _debug() { cerr << endl; }
template <class First, class... Rest>
void _debug(const First &first, const Rest &...rest) {
  cerr << first << " ";
  _debug(rest...);
}

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;

const double PI = (1 * acos(0.0));
const double EPS = 1e-9;
const double mod = 1e9 + 7;
const ll INF = 0x3f3f3f3f;
const ll INFL = 0x3f3f3f3f3f3f3f3fLL;

inline void finput(string filename) { freopen(filename.c_str(), "r", stdin); }

struct edge {
  int to;
  ll cost;
};

int N, Q, K;
vector<edge> g[100010];
ll d[100010];

void dijk(int s) {
  priority_queue<int> pq;
  pq.push(s);
  d[s] = 0;

  while (!pq.empty()) {
    int u = pq.top();
    pq.pop();
    for (edge v : g[u]) {
      if (d[v.to] > d[u] + v.cost) {
        d[v.to] = d[u] + v.cost;
        pq.push(v.to);
      }
    }
  }
}

int main() {
  ios_base::sync_with_stdio(0);
  // finput("./input");

  cin >> N;
  rep(i, N - 1) {
    int a, b;
    ll c;
    cin >> a >> b >> c;
    g[a].push_back({b, c});
    g[b].push_back({a, c});
  }

  cin >> Q >> K;
  fill(d, d + N + 1, INFL);
  dijk(K);

  rep(i, Q) {
    int x, y;
    cin >> x >> y;
    cout << d[x] + d[y] << endl;
  }

  return 0;
}