Problem p04003 (C++)

Buggy submission (status: Time Limit Exceeded):
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC optimize(3)
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC target("sse3", "sse2", "sse")
#pragma GCC target("avx", "sse4", "sse4.1", "sse4.2", "ssse3")
#pragma GCC target("f16c")
#pragma GCC optimize("inline", "fast-math", "unroll-loops",                    \
                     "no-stack-protector")
#pragma GCC diagnostic error "-fwhole-program"
#pragma GCC diagnostic error "-fcse-skip-blocks"
#pragma GCC diagnostic error "-funsafe-loop-optimizations"
#pragma GCC diagnostic error "-std=c++14"
#include "bits/stdc++.h"
// #include "ext/pb_ds/tree_policy.hpp"
// #include "ext/pb_ds/assoc_container.hpp"
#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fr(x) freopen(x, "r", stdin)
#define fw(x) freopen(x, "w", stdout)
#define iout(x) printf("%d\n", x)
#define lout(x) printf("%lld\n", x)
#define REP(x, l, u) for (ll x = l; x < u; x++)
#define RREP(x, l, u) for (ll x = l; x >= u; x--)
#define complete_unique(a) a.erase(unique(a.begin(), a.end()), a.end())
#define mst(x, a) memset(x, a, sizeof(x))
#define all(a) a.begin(), a.end()
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define MP make_pair
#define sqr(x) ((x) * (x))
#define lowbit(x) (x & (-x))
#define lson (ind << 1)
#define rson (ind << 1 | 1)
#define se second
#define fi first
#define dbg(x) cerr << #x << " = " << (x) << endl;
#define sz(x) ((int)x.size())
#define EX0 exit(0);

typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
using namespace std;
typedef vector<ll> VLL;
typedef vector<int> VI;
const int block_size = 320;
typedef complex<ll> point;
const ll mod = 1e9 + 7;
const ll inf = 1e9 + 7;
const ld eps = 1e-9;
const db PI = atan(1) * 4;
template <typename T> inline int sign(const T &a) {
  if (a < 0)
    return -1;
  if (a > 0)
    return 1;
  return 0;
}

template <typename T, typename S> inline bool upmin(T &a, const S &b) {
  return a > b ? a = b, 1 : 0;
}
template <typename T, typename S> inline bool upmax(T &a, const S &b) {
  return a < b ? a = b, 1 : 0;
}

template <typename T> inline void in(T &x) {
  x = 0;
  T f = 1;
  char ch = getchar();
  while (!isdigit(ch)) {
    if (ch == '-')
      f = -1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  x *= f;
}

ll twop(int x) { return 1LL << x; }

template <typename A, typename B> inline void in(A &x, B &y) {
  in(x);
  in(y);
}
template <typename A, typename B, typename C> inline void in(A &x, B &y, C &z) {
  in(x);
  in(y);
  in(z);
}
template <typename A, typename B, typename C, typename D>
inline void in(A &x, B &y, C &z, D &d) {
  in(x);
  in(y);
  in(z);
  in(d);
}
ll gcd(ll a, ll b) { return b == 0 ? a : gcd(b, a % b); }
namespace SOLVE {
void main() {}
} // namespace SOLVE

map<int, vector<int>> ed[1000010];
vector<PII> adj[100010];
int n, m;
int dis[100010];
set<PII> vis;
int original;
void dfs(priority_queue<pair<int, PII>, vector<pair<int, PII>>,
                        greater<pair<int, PII>>> &pq,
         int cur, int color) {
  for (auto neighbour : ed[color][cur]) {
    if (vis.count(MP(neighbour, color)) == 0) {
      if (dis[original] < dis[neighbour])
        pq.push(MP(dis[original], MP(neighbour, color)));
      vis.insert(MP(neighbour, color));
      dfs(pq, neighbour, color);
    }
  }
}
int main() {

  in(n, m);
  REP(i, 0, m) {
    int u, v, w;
    in(u, v, w);
    ed[w][u].PB(v);
    ed[w][v].PB(u);
    adj[u].PB(MP(v, w));
    adj[v].PB(MP(u, w));
  }
  mst(dis, 0x3f);

  priority_queue<pair<int, PII>, vector<pair<int, PII>>,
                 greater<pair<int, PII>>>
      pq;
  pq.push(MP(0, MP(1, 0)));
  while (sz(pq)) {
    auto color = pq.top().se.se, source = pq.top().se.fi, d = pq.top().fi;
    pq.pop();
    if (d < dis[source]) {
      dis[source] = d;
      original = source;
      vis.insert(MP(source, color));
      dfs(pq, source, color);
      for (auto neighbor : adj[source]) {
        pq.push(MP(d + 1, MP(neighbor.fi, neighbor.se)));
      }
    } else if (d == dis[source]) {
      vis.insert(MP(source, color));
      dfs(pq, source, color);
    }
  }

  if (dis[n] > 1000000)
    cout << -1;
  else
    cout << dis[n];

  return 0;
}


Fixed submission:
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC optimize(3)
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC target("sse3", "sse2", "sse")
#pragma GCC target("avx", "sse4", "sse4.1", "sse4.2", "ssse3")
#pragma GCC target("f16c")
#pragma GCC optimize("inline", "fast-math", "unroll-loops",                    \
                     "no-stack-protector")
#pragma GCC diagnostic error "-fwhole-program"
#pragma GCC diagnostic error "-fcse-skip-blocks"
#pragma GCC diagnostic error "-funsafe-loop-optimizations"
#pragma GCC diagnostic error "-std=c++14"
#include "bits/stdc++.h"
// #include "ext/pb_ds/tree_policy.hpp"
// #include "ext/pb_ds/assoc_container.hpp"
#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fr(x) freopen(x, "r", stdin)
#define fw(x) freopen(x, "w", stdout)
#define iout(x) printf("%d\n", x)
#define lout(x) printf("%lld\n", x)
#define REP(x, l, u) for (ll x = l; x < u; x++)
#define RREP(x, l, u) for (ll x = l; x >= u; x--)
#define complete_unique(a) a.erase(unique(a.begin(), a.end()), a.end())
#define mst(x, a) memset(x, a, sizeof(x))
#define all(a) a.begin(), a.end()
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define MP make_pair
#define sqr(x) ((x) * (x))
#define lowbit(x) (x & (-x))
#define lson (ind << 1)
#define rson (ind << 1 | 1)
#define se second
#define fi first
#define dbg(x) cerr << #x << " = " << (x) << endl;
#define sz(x) ((int)x.size())
#define EX0 exit(0);

typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ld;
using namespace std;
typedef vector<ll> VLL;
typedef vector<int> VI;
const int block_size = 320;
typedef complex<ll> point;
const ll mod = 1e9 + 7;
const ll inf = 1e9 + 7;
const ld eps = 1e-9;
const db PI = atan(1) * 4;
template <typename T> inline int sign(const T &a) {
  if (a < 0)
    return -1;
  if (a > 0)
    return 1;
  return 0;
}

template <typename T, typename S> inline bool upmin(T &a, const S &b) {
  return a > b ? a = b, 1 : 0;
}
template <typename T, typename S> inline bool upmax(T &a, const S &b) {
  return a < b ? a = b, 1 : 0;
}

template <typename T> inline void in(T &x) {
  x = 0;
  T f = 1;
  char ch = getchar();
  while (!isdigit(ch)) {
    if (ch == '-')
      f = -1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  x *= f;
}

ll twop(int x) { return 1LL << x; }

template <typename A, typename B> inline void in(A &x, B &y) {
  in(x);
  in(y);
}
template <typename A, typename B, typename C> inline void in(A &x, B &y, C &z) {
  in(x);
  in(y);
  in(z);
}
template <typename A, typename B, typename C, typename D>
inline void in(A &x, B &y, C &z, D &d) {
  in(x);
  in(y);
  in(z);
  in(d);
}
ll gcd(ll a, ll b) { return b == 0 ? a : gcd(b, a % b); }
namespace SOLVE {
void main() {}
} // namespace SOLVE

map<int, vector<int>> ed[1000010];
vector<PII> adj[100010];
int n, m;
int dis[100010];
set<PII> vis;
int original;
void dfs(priority_queue<pair<int, PII>, vector<pair<int, PII>>,
                        greater<pair<int, PII>>> &pq,
         int cur, int color) {
  for (auto neighbour : ed[color][cur]) {
    if (vis.count(MP(neighbour, color)) == 0) {
      if (dis[original] < dis[neighbour])
        pq.push(MP(dis[original], MP(neighbour, color)));
      vis.insert(MP(neighbour, color));
      dfs(pq, neighbour, color);
    }
  }
}
int main() {

  in(n, m);
  REP(i, 0, m) {
    int u, v, w;
    in(u, v, w);
    ed[w][u].PB(v);
    ed[w][v].PB(u);
    adj[u].PB(MP(v, w));
    adj[v].PB(MP(u, w));
  }
  mst(dis, 0x3f);

  priority_queue<pair<int, PII>, vector<pair<int, PII>>,
                 greater<pair<int, PII>>>
      pq;
  pq.push(MP(0, MP(1, 0)));
  while (sz(pq)) {
    auto color = pq.top().se.se, source = pq.top().se.fi, d = pq.top().fi;
    pq.pop();
    if (d < dis[source]) {
      dis[source] = d;
      original = source;
      vis.insert(MP(source, color));
      dfs(pq, source, color);
      for (auto neighbor : adj[source]) {
        pq.push(MP(d + 1, MP(neighbor.fi, neighbor.se)));
      }
    } else if (d == dis[source] && vis.count(MP(source, color)) == 0) {
      vis.insert(MP(source, color));
      dfs(pq, source, color);
    }
  }

  if (dis[n] > 1000000)
    cout << -1;
  else
    cout << dis[n];

  return 0;
}