Problem p00200 (C++) — buggy submission, verdict: Runtime Error

#include <algorithm>
#include <functional>
#include <iostream>
#include <list>
#include <queue>
#include <vector>
#define INF (1LL << 60)
using namespace std;
bool used[100];
long long dist[100];
void dijkstra(int V, int E, int s, vector<pair<int, long long>> X[]) {
  priority_queue<pair<long long, int>, vector<pair<long long, int>>,
                 greater<pair<long long, int>>>
      Q;
  for (int i = 0; i < V; i++)
    dist[i] = INF, used[i] = false;
  dist[s] = 0;
  Q.push(make_pair(0, s));
  int cnt = 0;
  while (!Q.empty()) {
    if (cnt > E)
      return; // NEGATIVE_CYCLE
    pair<long long, int> p = Q.top();
    used[p.second] = true;
    Q.pop();
    for (int i = 0; i < X[p.second].size(); i++) {
      int to = X[p.second][i].first;
      long long leng = X[p.second][i].second;
      if (dist[to] > dist[p.second] + leng && !used[to]) {
        dist[to] = dist[p.second] + leng;
        Q.push(make_pair(dist[to], to));
      }
    }
  }
}
int n, m, q, a, b, c, u, v, w1, w2;
vector<pair<int, long long>> G1[100], G2[100];
int main() {
  while (cin >> n >> m, n) {
    for (int i = 0; i < m; i++)
      G1[i].clear(), G2[i].clear();
    for (int i = 0; i < n; i++) {
      cin >> u >> v >> w1 >> w2;
      u--, v--;
      G1[u].push_back(make_pair(v, w1));
      G1[v].push_back(make_pair(u, w1));
      G2[u].push_back(make_pair(v, w2));
      G2[v].push_back(make_pair(u, w2));
    }
    cin >> q;
    for (int i = 0; i < q; i++) {
      cin >> a >> b >> c;
      a--, b--;
      if (c == 0) {
        dijkstra(m, n, a, G1);
        cout << dist[b] << endl;
      } else {
        dijkstra(m, n, a, G2);
        cout << dist[b] << endl;
      }
    }
  }
}

Error: WA

Fixed submission:

#include <algorithm>
#include <functional>
#include <iostream>
#include <list>
#include <queue>
#include <vector>
#define INF (1LL << 60)
using namespace std;
bool used[100];
long long dist[100];
void dijkstra(int V, int E, int s, vector<pair<int, long long>> X[]) {
  priority_queue<pair<long long, int>, vector<pair<long long, int>>,
                 greater<pair<long long, int>>>
      Q;
  for (int i = 0; i < V; i++)
    dist[i] = INF, used[i] = false;
  dist[s] = 0;
  Q.push(make_pair(0, s));
  int cnt = 0;
  while (!Q.empty()) {
    if (cnt > E)
      return; // NEGATIVE_CYCLE
    pair<long long, int> p = Q.top();
    used[p.second] = true;
    Q.pop();
    for (int i = 0; i < X[p.second].size(); i++) {
      int to = X[p.second][i].first;
      long long leng = X[p.second][i].second;
      if (dist[to] > dist[p.second] + leng && !used[to]) {
        dist[to] = dist[p.second] + leng;
        Q.push(make_pair(dist[to], to));
      }
    }
  }
}
int n, m, q, a, b, c, u, v, w1, w2;
vector<pair<int, long long>> G1[100], G2[100];
int main() {
  while (cin >> n >> m, n) {
    for (int i = 0; i < m; i++)
      G1[i].clear(), G2[i].clear();
    for (int i = 0; i < n; i++) {
      cin >> u >> v >> w1 >> w2;
      G1[u].push_back(make_pair(v, w1));
      G1[v].push_back(make_pair(u, w1));
      G2[u].push_back(make_pair(v, w2));
      G2[v].push_back(make_pair(u, w2));
    }
    cin >> q;
    for (int i = 0; i < q; i++) {
      cin >> a >> b >> c;
      if (c == 0) {
        dijkstra(m, n, a, G1);
        cout << dist[b] << endl;
      } else {
        dijkstra(m, n, a, G2);
        cout << dist[b] << endl;
      }
    }
  }
}