Problem p01449 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <complex>
#include <cstdio>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

// common

typedef int i32;
typedef long long i64, ll;
typedef long double ld;

#define BR "\\n"
#define ALL(c) (c).begin(), (c).end()
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define FOR(i, l, r) for (int i = (int)l; i < (int)(r); ++i)
#define EACH(it, o) for (auto it = (o).begin(); it != (o).end(); ++it)
#define IN(l, v, r) ((l) <= (v) && (v) < (r))

// config
// #define NDEBUG
// #define INF 1<<30
// #define EPS 1e-8
// const ll MOD =100000007;

// debug
#ifdef NDEBUG
#define DUMP(x)
#define DUMPLN(x)
#define DEBUG(x)
#define DEBUGLN(x)
#define LINE()
#define LINELN()
#define CHECK(exp, act)
#define STOP(e)
#else
#define DUMP(x) cerr << #x << " = " << (x)
#define DUMPLN(x) DUMP(x) << endl
#define DEBUG(x) DUMP(x) << LINE() << " " << __FILE__
#define DEBUGLN(x) DEBUG(x) << endl
#define LINE() cerr << " (L" << __LINE__ << ")"
#define LINELN() LINE() << endl
#define CHECK(exp, act)                                                        \\
  if (exp != act) {                                                            \\
    DUMPLN(exp);                                                               \\
    DEBUGLN(act);                                                              \\
  }
#define STOP(e)                                                                \\
  CHECK(e, true);                                                              \\
  if (!(e))                                                                    \\
    exit(1);
#endif

template <class T> inline string toString(const vector<T> &x) {
  stringstream ss;
  REP(i, x.size()) {
    if (i != 0)
      ss << " ";
    ss << x[i];
  }
  return ss.str();
}

template <class T> inline string toString(const vector<vector<T>> &map) {
  stringstream ss;
  REP(i, map.size()) {
    if (i != 0)
      ss << BR;
    ss << toString(map[i]);
  }
  return ss.str();
}
template <class K, class V> string toString(map<K, V> &x) {
  string res;
  stringstream ss;
  for (auto &p : x)
    ss << p.first << ":" << p.second << " ";
  return ss.str();
}

string BITtoString(int bit) {
  stringstream ss;
  while (bit != 0) {
    ss << (bit % 2);
    bit /= 2;
  }
  string res = ss.str();
  reverse(ALL(res));
  return res;
}

template <typename T, typename V> inline T pmod(T v, V MOD) {
  return (v % MOD + MOD) % MOD;
}
#define nextInt(n) scanf("%d", &n)
#define defInt(n)                                                              \\
  int n;                                                                       \\
  nextInt(n)
#define nextLong(n) scanf("%lld", &n)
#define defLong(n)                                                             \\
  ll n;                                                                        \\
  nextLong(n)
#define nextDouble(n) scanf("%lf", &n)

struct UnionFind {
  vector<int> par;  // 親
  vector<int> rank; // 木の深さ
  vector<int> ss;   // xの属する集合のサイズ
  int size;         // 集合の個数
  UnionFind(int n) {
    REP(i, n) par.push_back(i);
    rank = vector<int>(n);
    ss = vector<int>(n, 1);
    size = n;
  }
  int root(int x) {
    if (par[x] == x)
      return x;
    return par[x] = root(par[x]);
  }
  bool same(int x, int y) { return root(x) == root(y); }
  void unite(int x, int y) {
    x = root(x);
    y = root(y);
    if (x == y)
      return;
    if (rank[x] < rank[y]) {
      par[x] = y;
      ss[y] += ss[x];
    } else {
      par[y] = x;
      ss[x] += ss[y];
    }
    if (rank[x] == rank[y])
      rank[x]++;
    size--;
  }
  int getS(int x) { return ss[root(x)]; }
};

int INF = 1 << 28;
class Main {
public:
  int N;
  vector<int> ps;
  vector<int> ds;
  void run() {
    // ifstream cin("D2");
    //		ofstream cout( "D2.out" );

    cin >> N;
    ps = vector<int>(N);
    REP(i, N) cin >> ps[i];
    UnionFind uf(N);
    REP(i, N) uf.unite(i, max(min(i + ps[i], N - 1), 0));
    // どれかが0ならセーフ
    vector<int> ms(N, -1);
    REP(i, N) if (ps[i] == 0) ms[uf.root(i)] = i;
    ds = vector<int>(N, INF);

    priority_queue<pair<int, int>, vector<pair<int, int>>,
                   greater<pair<int, int>>>
        que;
    ds[0] = 0;
    que.push(make_pair(0, 0));
    vector<bool> passed(N);
    while (!que.empty()) {
      pair<int, int> v = que.top();
      que.pop();
      if (passed[v.second])
        continue;
      passed[v.second] = true;
      for (int d = 1; d <= 6; d++) {
        int nv = v.second + d;
        nv = max(min(nv, N - 1), 0);
        if (ms[uf.root(nv)] != -1 && ds[ms[uf.root(nv)]] > ds[v.second] + 1) {
          ds[ms[uf.root(nv)]] = ds[v.second] + 1;
          que.push(make_pair(ds[ms[uf.root(nv)]], ms[uf.root(nv)]));
        }
      }
    }

    cout << ds[N - 1] << endl;
  }
};
int main() {
  cout << fixed << setprecision(15);
  ios::sync_with_stdio(false);
  Main().run();
  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <complex>
#include <cstdio>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

// common

typedef int i32;
typedef long long i64, ll;
typedef long double ld;

#define BR "\\n"
#define ALL(c) (c).begin(), (c).end()
#define REP(i, n) for (int i = 0; i < (int)(n); ++i)
#define FOR(i, l, r) for (int i = (int)l; i < (int)(r); ++i)
#define EACH(it, o) for (auto it = (o).begin(); it != (o).end(); ++it)
#define IN(l, v, r) ((l) <= (v) && (v) < (r))

// config
// #define NDEBUG
// #define INF 1<<30
// #define EPS 1e-8
// const ll MOD =100000007;

// debug
#ifdef NDEBUG
#define DUMP(x)
#define DUMPLN(x)
#define DEBUG(x)
#define DEBUGLN(x)
#define LINE()
#define LINELN()
#define CHECK(exp, act)
#define STOP(e)
#else
#define DUMP(x) cerr << #x << " = " << (x)
#define DUMPLN(x) DUMP(x) << endl
#define DEBUG(x) DUMP(x) << LINE() << " " << __FILE__
#define DEBUGLN(x) DEBUG(x) << endl
#define LINE() cerr << " (L" << __LINE__ << ")"
#define LINELN() LINE() << endl
#define CHECK(exp, act)                                                        \\
  if (exp != act) {                                                            \\
    DUMPLN(exp);                                                               \\
    DEBUGLN(act);                                                              \\
  }
#define STOP(e)                                                                \\
  CHECK(e, true);                                                              \\
  if (!(e))                                                                    \\
    exit(1);
#endif

template <class T> inline string toString(const vector<T> &x) {
  stringstream ss;
  REP(i, x.size()) {
    if (i != 0)
      ss << " ";
    ss << x[i];
  }
  return ss.str();
}

template <class T> inline string toString(const vector<vector<T>> &map) {
  stringstream ss;
  REP(i, map.size()) {
    if (i != 0)
      ss << BR;
    ss << toString(map[i]);
  }
  return ss.str();
}
template <class K, class V> string toString(map<K, V> &x) {
  string res;
  stringstream ss;
  for (auto &p : x)
    ss << p.first << ":" << p.second << " ";
  return ss.str();
}

string BITtoString(int bit) {
  stringstream ss;
  while (bit != 0) {
    ss << (bit % 2);
    bit /= 2;
  }
  string res = ss.str();
  reverse(ALL(res));
  return res;
}

template <typename T, typename V> inline T pmod(T v, V MOD) {
  return (v % MOD + MOD) % MOD;
}
#define nextInt(n) scanf("%d", &n)
#define defInt(n)                                                              \\
  int n;                                                                       \\
  nextInt(n)
#define nextLong(n) scanf("%lld", &n)
#define defLong(n)                                                             \\
  ll n;                                                                        \\
  nextLong(n)
#define nextDouble(n) scanf("%lf", &n)

struct UnionFind {
  vector<int> par;  // 親
  vector<int> rank; // 木の深さ
  vector<int> ss;   // xの属する集合のサイズ
  int size;         // 集合の個数
  UnionFind(int n) {
    REP(i, n) par.push_back(i);
    rank = vector<int>(n);
    ss = vector<int>(n, 1);
    size = n;
  }
  int root(int x) {
    if (par[x] == x)
      return x;
    return par[x] = root(par[x]);
  }
  bool same(int x, int y) { return root(x) == root(y); }
  void unite(int x, int y) {
    x = root(x);
    y = root(y);
    if (x == y)
      return;
    if (rank[x] < rank[y]) {
      par[x] = y;
      ss[y] += ss[x];
    } else {
      par[y] = x;
      ss[x] += ss[y];
    }
    if (rank[x] == rank[y])
      rank[x]++;
    size--;
  }
  int getS(int x) { return ss[root(x)]; }
};

int INF = 1 << 28;
class Main {
public:
  int N;
  vector<int> ps;

  vector<int> ds;
  void run() {
    // ifstream cin("D2");
    //		ofstream cout( "D2.out" );

    while (true) {
      cin >> N;
      if (N == 0)
        break;
      ps = vector<int>(N);
      REP(i, N) cin >> ps[i];
      UnionFind uf(N);
      REP(i, N) uf.unite(i, max(min(i + ps[i], N - 1), 0));
      // どれかが0ならセーフ
      vector<int> ms(N, -1);
      REP(i, N) if (ps[i] == 0) ms[uf.root(i)] = i;
      //			DUMP(toString(ms));

      ds = vector<int>(N, INF);

      priority_queue<int, vector<int>, greater<int>> que;
      ds[0] = 0;
      que.push(0);
      vector<bool> passed(N);
      while (!que.empty()) {
        int v = que.top();
        que.pop();
        if (passed[v])
          continue;
        passed[v] = true;
        for (int d = 1; d <= 6; d++) {
          int nv = v + d;
          nv = max(min(nv, N - 1), 0);
          if (ms[uf.root(nv)] != -1 && ds[ms[uf.root(nv)]] > ds[v] + 1) {
            ds[ms[uf.root(nv)]] = ds[v] + 1;
            que.push(ms[uf.root(nv)]);
          }
        }
      }
      //			DUMP(toString(ds));

      cout << ds[N - 1] << endl;
    }
  }
};
int main() {
  cout << fixed << setprecision(15);
  ios::sync_with_stdio(false);
  Main().run();
  return 0;
}