Problem p04003 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#include <unordered_map>
#include <unordered_set>

using namespace std;

#define all(c) ((c).begin()), ((c).end())
#define dump(c) cerr << "> " << #c << " = " << (c) << endl;
#define iter(c) __typeof((c).begin())
#define tr(i, c) for (iter(c) i = (c).begin(); i != (c).end(); i++)
#define REP(i, a, b) for (int i = a; i < (int)(b); i++)
#define rep(i, n) REP(i, 0, n)
#define mp make_pair
#define fst first
#define snd second
#define pb push_back
#define debug(fmt, ...) fprintf(stderr, fmt "\n", ##__VA_ARGS__)

typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int INF = 1 << 30;
const double EPS = 1e-10;

double zero(double d) { return d < EPS ? 0.0 : d; }
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << '(' << p.first << ',' << p.second << ')';
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &a) {
  os << '[';
  rep(i, a.size()) os << (i ? " " : "") << a[i];
  return os << ']';
}

string toString(int i) {
  stringstream ss;
  ss << i;
  return ss.str();
}

const int MOD = 1000000007;
// a^k
ll fpow(ll a, ll k, int M) {
  ll res = 1ll;
  ll x = a;
  while (k != 0) {
    if ((k & 1) == 1)
      res = (res * x) % M;
    x = (x * x) % M;
    k >>= 1;
  }
  return res;
}

struct prepare {
  prepare() {
    cout.setf(ios::fixed, ios::floatfield);
    cout.precision(8);
    ios_base::sync_with_stdio(false);
  }
} _prepare;

ll pl(ll a, ll b) { return a * ((ll)1e6 + 10) + b; }

using edge = pair<ll, int>;

int dijkstra(int start, int goal, map<ll, vector<edge>> &graphs) {
  priority_queue<pair<int, ll>, vector<pair<int, ll>>, greater<pair<int, ll>>>
      que;
  map<ll, int> d;
  d[pl(start, 0)] = 0;
  que.push(mp(0, pl(start, 0)));

  while (!que.empty()) {
    pair<int, ll> p2 = que.top();
    que.pop();
    int p = p2.first;
    ll v = p2.second;

    if (d[v] == 0 && v != pl(start, 0))
      d[v] = INF;
    if (d[v] < p)
      continue;

    tr(it, graphs[v]) {
      const ll to = it->first;
      const int cost = it->second;
      if (d[to] == 0 && to != pl(start, 0))
        d[to] = INF;

      if (d[to] > d[v] + cost) {
        d[to] = d[v] + cost;
        que.push(mp(d[to], to));
      }
    }
  }

  return d[pl(goal, 0)];
}

int main() {
  int N, M;
  cin >> N >> M;

  map<ll, vector<edge>> graph;
  while (M--) {
    int p, q, c;
    cin >> p >> q >> c;
    --p, --q;

    graph[pl(p, c)].push_back(mp(pl(q, c), 0));
    graph[pl(q, c)].push_back(mp(pl(p, c), 0));

    // core station
    graph[pl(p, c)].push_back(mp(pl(p, 0), 0));
    graph[pl(p, 0)].push_back(mp(pl(p, c), 1));
    graph[pl(q, c)].push_back(mp(pl(q, 0), 0));
    graph[pl(q, 0)].push_back(mp(pl(q, c), 1));
  }

  int d = dijkstra(0, N - 1, graph);
  if (d == 0)
    cout << -1 << endl;
  else
    cout << d << endl;

  return 0;
}


Fixed submission:
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#include <unordered_map>
#include <unordered_set>

using namespace std;

#define all(c) ((c).begin()), ((c).end())
#define dump(c) cerr << "> " << #c << " = " << (c) << endl;
#define iter(c) __typeof((c).begin())
#define tr(i, c) for (iter(c) i = (c).begin(); i != (c).end(); i++)
#define REP(i, a, b) for (int i = a; i < (int)(b); i++)
#define rep(i, n) REP(i, 0, n)
#define mp make_pair
#define fst first
#define snd second
#define pb push_back
#define debug(fmt, ...) fprintf(stderr, fmt "\n", ##__VA_ARGS__)

typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int INF = 1 << 30;
const double EPS = 1e-10;

double zero(double d) { return d < EPS ? 0.0 : d; }
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return true;
  }
  return false;
}
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  return os << '(' << p.first << ',' << p.second << ')';
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &a) {
  os << '[';
  rep(i, a.size()) os << (i ? " " : "") << a[i];
  return os << ']';
}

string toString(int i) {
  stringstream ss;
  ss << i;
  return ss.str();
}

const int MOD = 1000000007;
// a^k
ll fpow(ll a, ll k, int M) {
  ll res = 1ll;
  ll x = a;
  while (k != 0) {
    if ((k & 1) == 1)
      res = (res * x) % M;
    x = (x * x) % M;
    k >>= 1;
  }
  return res;
}

struct prepare {
  prepare() {
    cout.setf(ios::fixed, ios::floatfield);
    cout.precision(8);
    ios_base::sync_with_stdio(false);
  }
} _prepare;

ll pl(ll a, ll b) { return a * ((ll)1e6 + 10) + b; }

using edge = pair<ll, int>;

int dijkstra(int start, int goal, map<ll, vector<edge>> &graphs) {
  priority_queue<pair<int, ll>, vector<pair<int, ll>>, greater<pair<int, ll>>>
      que;
  unordered_map<ll, int> d;
  d[pl(start, 0)] = 0;
  que.push(mp(0, pl(start, 0)));

  while (!que.empty()) {
    pair<int, ll> p2 = que.top();
    que.pop();
    int p = p2.first;
    ll v = p2.second;

    if (d[v] == 0 && v != pl(start, 0))
      d[v] = INF;
    if (d[v] < p)
      continue;

    tr(it, graphs[v]) {
      const ll to = it->first;
      const int cost = it->second;
      if (d[to] == 0 && to != pl(start, 0))
        d[to] = INF;

      if (d[to] > d[v] + cost) {
        d[to] = d[v] + cost;
        que.push(mp(d[to], to));
      }
    }
  }

  return d[pl(goal, 0)];
}

int main() {
  int N, M;
  cin >> N >> M;

  map<ll, vector<edge>> graph;
  while (M--) {
    int p, q, c;
    cin >> p >> q >> c;
    --p, --q;

    graph[pl(p, c)].push_back(mp(pl(q, c), 0));
    graph[pl(q, c)].push_back(mp(pl(p, c), 0));

    // core station
    graph[pl(p, c)].push_back(mp(pl(p, 0), 0));
    graph[pl(p, 0)].push_back(mp(pl(p, c), 1));
    graph[pl(q, c)].push_back(mp(pl(q, 0), 0));
    graph[pl(q, 0)].push_back(mp(pl(q, c), 1));
  }

  int d = dijkstra(0, N - 1, graph);
  if (d == 0)
    cout << -1 << endl;
  else
    cout << d << endl;

  return 0;
}