Problem p04003 (C++)

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

using VS = vector<string>;
using LL = long long;
using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;
using PLL = pair<LL, LL>;
using VL = vector<LL>;
using VVL = vector<VL>;

#define ALL(a) begin((a)), end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define SZ(a) int((a).size())
#define SORT(c) sort(ALL((c)))
#define RSORT(c) sort(RALL((c)))
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))
#define FOR(i, s, e) for (int(i) = (s); (i) < (e); (i)++)
#define FORR(i, s, e) for (int(i) = (s); (i) > (e); (i)--)
// #pragma GCC optimize ("-O3")
#ifdef YANG33
#include "mydebug.hpp"
#else
#define DD(x)
#endif
const int INF = 1e9;
const LL LINF = 1e16;
const LL MOD = 1000000007;
const double PI = acos(-1.0);
int DX[8] = {0, 0, 1, -1, 1, 1, -1, -1};
int DY[8] = {1, -1, 0, 0, 1, -1, 1, -1};

/* -----  __MAKE_TIME__  Problem: __PROBLEM__ / Link: __CONTEST_URL__  ----- */
/* ------問題------



-----問題ここまで----- */
/* -----解説等-----



----解説ここまで---- */

struct UnionFind {
  vector<int> data;
  UnionFind() {}
  UnionFind(int n) { data.assign(n, -1); }
  bool unionSet(int x, int y) {
    x = root(x);
    y = root(y);
    if (x != y) {
      if (data[y] < data[x])
        swap(x, y);
      data[x] += data[y];
      data[y] = x;
    }
    return x != y;
  }
  bool same(int x, int y) { return root(x) == root(y); }
  int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
  int size(int x) { return -data[root(x)]; }
};

auto f(const vector<PII> &edge) {

  int id = 0;
  map<int, int> M;
  {
    for (const auto &it : edge) {
      if (M.find(it.first) == M.end()) {
        M[it.first] = id++;
      }
      if (M.find(it.second) == M.end()) {
        M[it.second] = id++;
      }
    }
  }
  const int sz = id;
  UnionFind uf(sz);
  map<int, int> roots;
  for (const auto &it : edge) {
    uf.unionSet(M[it.first], M[it.second]);
  }
  int rootid = 0;
  for (const auto &it : edge) {
    if (roots.find(uf.root(M[it.first])) == roots.end()) {
      roots[uf.root(M[it.first])] = rootid++;
    }
    // if (roots.find(uf.root(M[it.second])) == roots.end()) {
    //	// これはあってはならない
    //	assert(0);
    //	roots[uf.root(M[it.second])] = rootid++;
    //  }
  }

  vector<vector<PII>> res(rootid);
  for (const auto &it : edge) {
    res[roots[uf.root(M[it.first])]].push_back(it);
  }
  return res;
}

VL Dijkstra(vector<vector<PLL>> &G, int s) {
  VL dist(SZ(G), LINF);
  dist[s] = 0;
  priority_queue<PLL, vector<PLL>, greater<PLL>> que;
  que.push(PLL(0LL, s));

  while (!que.empty()) {
    PLL p = que.top();
    que.pop();
    int v;       /* 頂点*/
    long long d; /* 頂点vまでの距離 */
    tie(d, v) = p;

    if (d > dist[v])
      continue;

    FOR(i, 0, (int)G[v].size()) {
      int nv = G[v][i].first;
      if (dist[nv] > dist[v] + G[v][i].second) {
        dist[nv] = dist[v] + G[v][i].second;
        que.push(PLL(dist[nv], nv));
      }
    }
  }
  return dist;
}
int read() {
  int in;
  scanf("%d", &in);
  return in;
}

int main() {
  LL N = read(), M = read();

  vector<vector<PII>> Cedge(1e6);
  FOR(i, 0, M) {
    int p = read() - 1, q = read() - 1, c = read() - 1;
    Cedge[c].push_back(PII(p, q));
  }
  vector<vector<PLL>> G(N + 1e6); // 2Nでいい?
  int cid = N;

  bitset<100000> used;
  FOR(c, 0, 1e6) {
    auto res = f(Cedge[c]);
    for (auto subedges : res) {
      for (auto e : subedges) {
        used[e.first] = 0;
        used[e.second] = 0;
      }
    }

    for (auto subedges : res) {
      for (auto e : subedges) {
        if (!used[e.first]) {
          G[cid].push_back(PLL(e.first, 1));
          G[e.first].push_back(PLL(cid, 1));
          used[e.first] = 1;
        }
        if (!used[e.second]) {
          G[cid].push_back(PLL(e.second, 1));
          G[e.second].push_back(PLL(cid, 1));
          used[e.second] = 1;
        }
      }
      cid++;
    }
  }
  assert(cid < 250000);
  auto res = Dijkstra(G, 0);
  LL ans = res[N - 1] / 2;
  if (ans == LINF / 2)
    ans = -1;
  cout << ans << "\n";

  return 0;
}

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

using VS = vector<string>;
using LL = long long;
using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;
using PLL = pair<LL, LL>;
using VL = vector<LL>;
using VVL = vector<VL>;

#define ALL(a) begin((a)), end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define SZ(a) int((a).size())
#define SORT(c) sort(ALL((c)))
#define RSORT(c) sort(RALL((c)))
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))
#define FOR(i, s, e) for (int(i) = (s); (i) < (e); (i)++)
#define FORR(i, s, e) for (int(i) = (s); (i) > (e); (i)--)
// #pragma GCC optimize ("-O3")
#ifdef YANG33
#include "mydebug.hpp"
#else
#define DD(x)
#endif
const int INF = 1e9;
const LL LINF = 1e16;
const LL MOD = 1000000007;
const double PI = acos(-1.0);
int DX[8] = {0, 0, 1, -1, 1, 1, -1, -1};
int DY[8] = {1, -1, 0, 0, 1, -1, 1, -1};

/* -----  __MAKE_TIME__  Problem: __PROBLEM__ / Link: __CONTEST_URL__  ----- */
/* ------問題------



-----問題ここまで----- */
/* -----解説等-----



----解説ここまで---- */

struct UnionFind {
  vector<int> data;
  UnionFind() {}
  UnionFind(int n) { data.assign(n, -1); }
  bool unionSet(int x, int y) {
    x = root(x);
    y = root(y);
    if (x != y) {
      if (data[y] < data[x])
        swap(x, y);
      data[x] += data[y];
      data[y] = x;
    }
    return x != y;
  }
  bool same(int x, int y) { return root(x) == root(y); }
  int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
  int size(int x) { return -data[root(x)]; }
};

auto f(const vector<PII> &edge) {

  int id = 0;
  map<int, int> M;
  {
    for (const auto &it : edge) {
      if (M.find(it.first) == M.end()) {
        M[it.first] = id++;
      }
      if (M.find(it.second) == M.end()) {
        M[it.second] = id++;
      }
    }
  }
  const int sz = id;
  UnionFind uf(sz);
  map<int, int> roots;
  for (const auto &it : edge) {
    uf.unionSet(M[it.first], M[it.second]);
  }
  int rootid = 0;
  for (const auto &it : edge) {
    if (roots.find(uf.root(M[it.first])) == roots.end()) {
      roots[uf.root(M[it.first])] = rootid++;
    }
    // if (roots.find(uf.root(M[it.second])) == roots.end()) {
    //	// これはあってはならない
    //	assert(0);
    //	roots[uf.root(M[it.second])] = rootid++;
    //  }
  }

  vector<vector<PII>> res(rootid);
  for (const auto &it : edge) {
    res[roots[uf.root(M[it.first])]].push_back(it);
  }
  return res;
}

VL Dijkstra(vector<vector<PLL>> &G, int s) {
  VL dist(SZ(G), LINF);
  dist[s] = 0;
  priority_queue<PLL, vector<PLL>, greater<PLL>> que;
  que.push(PLL(0LL, s));

  while (!que.empty()) {
    PLL p = que.top();
    que.pop();
    int v;       /* 頂点*/
    long long d; /* 頂点vまでの距離 */
    tie(d, v) = p;

    if (d > dist[v])
      continue;

    FOR(i, 0, (int)G[v].size()) {
      int nv = G[v][i].first;
      if (dist[nv] > dist[v] + G[v][i].second) {
        dist[nv] = dist[v] + G[v][i].second;
        que.push(PLL(dist[nv], nv));
      }
    }
  }
  return dist;
}
int read() {
  int in;
  scanf("%d", &in);
  return in;
}

int main() {
  LL N = read(), M = read();

  vector<vector<PII>> Cedge(1e6);
  FOR(i, 0, M) {
    int p = read() - 1, q = read() - 1, c = read() - 1;
    Cedge[c].push_back(PII(p, q));
  }
  vector<vector<PLL>> G(N + 1e6); // 2Nでいい?
  int cid = N;

  bitset<100000> used;
  FOR(c, 0, 1e6) {
    auto res = f(Cedge[c]);
    for (auto subedges : res) {
      for (auto e : subedges) {
        used[e.first] = 0;
        used[e.second] = 0;
      }
    }

    for (auto subedges : res) {
      for (auto e : subedges) {
        if (!used[e.first]) {
          G[cid].push_back(PLL(e.first, 1));
          G[e.first].push_back(PLL(cid, 1));
          used[e.first] = 1;
        }
        if (!used[e.second]) {
          G[cid].push_back(PLL(e.second, 1));
          G[e.second].push_back(PLL(cid, 1));
          used[e.second] = 1;
        }
      }
      cid++;
    }
  }
  assert(cid < 400000);
  auto res = Dijkstra(G, 0);
  LL ans = res[N - 1] / 2;
  if (ans == LINF / 2)
    ans = -1;
  cout << ans << "\n";

  return 0;
}