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

#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;
using namespace placeholders;

typedef long long LL;
typedef unsigned long long ULL;
typedef vector<int> VI;
typedef vector<vector<int>> VVI;
typedef vector<string> VS;
typedef stringstream SS;
typedef pair<int, int> PII;
typedef vector<pair<int, int>> VPII;
#define VT(T) vector<T>
#define VVT(T) vector<vector<T>>
#define LIM(T) numeric_limits<T>

template <typename T> inline istream &operator>>(istream &s, vector<T> &v) {
  for (T &t : v) {
    s >> t;
  }
  return s;
}
template <typename T>
inline ostream &operator<<(ostream &s, const vector<T> &v) {
  for (int i = 0; i < int(v.size()); ++i) {
    s << (" " + !i) << v[i];
  }
  return s;
}
template <typename T> inline T fromString(const string &s) {
  T res;
  istringstream iss(s);
  iss >> res;
  return res;
};
template <typename T> inline string toString(const T &a) {
  ostringstream oss;
  oss << a;
  return oss.str();
};

#define REP2(i, n) REP3(i, 0, n)
#define REP3(i, m, n) for (int i = (int)(m); i < (int)(n); ++i)
#define GET_REP(a, b, c, F, ...) F
#define REP(...) GET_REP(__VA_ARGS__, REP3, REP2)(__VA_ARGS__)
#define FOR(e, c) for (auto &e : c)
#define ALL(c) (c).begin(), (c).end()
#define AALL(a, t) (t *)a, (t *)a + sizeof(a) / sizeof(t)
#define DRANGE(c, p) (c).begin(), (c).begin() + p, (c).end()

#define SZ(v) ((int)(v).size())
#define PB push_back
#define EM emplace
#define EB emplace_back
#define BI back_inserter

#define EXIST(c, e) ((c).find(e) != (c).end())

#define MP make_pair
#define fst first
#define snd second

#define DUMP(x) cerr << #x << " = " << (x) << endl

constexpr int INF = LIM(int)::max();

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  for (int N; cin >> N && N;) {
    VI ps(N);
    cin >> ps;

    VI distances(N, INF);
    distances[0] = 0;

    queue<int> que;
    que.push(0);

    VI jump(N, -1);

    while (!que.empty()) {
      const int cur = que.front();
      que.pop();

      REP(i, 1, 7) {
        bool ok = true;
        int nex = cur + i;

        if (N <= nex) {
          break;
        }

        if (ps[nex] == 0) {
        } else if (jump[nex] == -2) {
          ok = false;
        } else if (jump[nex] != -1) {
          nex = jump[nex];
        } else {
          set<int> visited;
          while (ps[nex]) {
            visited.insert(nex);
            nex += ps[nex];

            if (EXIST(visited, nex)) {
              ok = false;
              break;
            }
          }

          FOR(vis, visited) { jump[vis] = ok ? nex : -2; }
        }

        if (ok && distances[cur] + 1 < distances[nex]) {
          distances[nex] = distances[cur] + 1;
          que.push(nex);
        }
      }
    }

    cout << distances.back() << endl;
  }

  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;
using namespace placeholders;

typedef long long LL;
typedef unsigned long long ULL;
typedef vector<int> VI;
typedef vector<vector<int>> VVI;
typedef vector<string> VS;
typedef stringstream SS;
typedef pair<int, int> PII;
typedef vector<pair<int, int>> VPII;
#define VT(T) vector<T>
#define VVT(T) vector<vector<T>>
#define LIM(T) numeric_limits<T>

template <typename T> inline istream &operator>>(istream &s, vector<T> &v) {
  for (T &t : v) {
    s >> t;
  }
  return s;
}
template <typename T>
inline ostream &operator<<(ostream &s, const vector<T> &v) {
  for (int i = 0; i < int(v.size()); ++i) {
    s << (" " + !i) << v[i];
  }
  return s;
}
template <typename T> inline T fromString(const string &s) {
  T res;
  istringstream iss(s);
  iss >> res;
  return res;
};
template <typename T> inline string toString(const T &a) {
  ostringstream oss;
  oss << a;
  return oss.str();
};

#define REP2(i, n) REP3(i, 0, n)
#define REP3(i, m, n) for (int i = (int)(m); i < (int)(n); ++i)
#define GET_REP(a, b, c, F, ...) F
#define REP(...) GET_REP(__VA_ARGS__, REP3, REP2)(__VA_ARGS__)
#define FOR(e, c) for (auto &e : c)
#define ALL(c) (c).begin(), (c).end()
#define AALL(a, t) (t *)a, (t *)a + sizeof(a) / sizeof(t)
#define DRANGE(c, p) (c).begin(), (c).begin() + p, (c).end()

#define SZ(v) ((int)(v).size())
#define PB push_back
#define EM emplace
#define EB emplace_back
#define BI back_inserter

#define EXIST(c, e) ((c).find(e) != (c).end())

#define MP make_pair
#define fst first
#define snd second

#define DUMP(x) cerr << #x << " = " << (x) << endl

constexpr int INF = LIM(int)::max();

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  for (int N; cin >> N && N;) {
    VI ps(N);
    cin >> ps;

    VI distances(N, INF);
    distances[0] = 0;

    queue<int> que;
    que.push(0);

    VI jump(N, -1);

    while (!que.empty()) {
      const int cur = que.front();
      que.pop();

      REP(i, 1, 7) {
        bool ok = true;
        int nex = cur + i;

        if (N <= nex) {
          break;
        }

        if (ps[nex] == 0) {
        } else if (jump[nex] != -1) {
          nex = jump[nex];
        } else {
          set<int> visited;
          while (ps[nex]) {
            visited.insert(nex);
            nex += ps[nex];

            if (EXIST(visited, nex)) {
              ok = false;
              break;
            }
          }

          if (ok) {
            FOR(vis, visited) { jump[vis] = nex; }
          }
        }

        if (ok && distances[cur] + 1 < distances[nex]) {
          distances[nex] = distances[cur] + 1;
          que.push(nex);
        }
      }
    }

    cout << distances.back() << endl;
  }

  return 0;
}