Problem p02884 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdint>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <regex>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;
using ll = long long;
using ull = unsigned long long;

constexpr ll INF = 1'000'000'000'000'000'000;
namespace utils {
#define ALL(x) begin(x), end(x)
#define RALL(x) rbegin(x), rend(x)
template <class T, class Compare>
using p_queue = priority_queue<T, vector<T>, Compare>;
template <class T> using min_queue = p_queue<T, greater<T>>;
template <class T> using max_queue = p_queue<T, less<T>>;

template <class T> bool up_min(T &X, const T &A) {
  if (X > A) {
    X = A;
    return true;
  }
  return false;
}
template <class T> bool up_max(T &X, const T &A) {
  if (X < A) {
    X = A;
    return true;
  }
  return false;
}

ll operator"" _64(unsigned long long x) { return ll(x); }
ull operator"" _64u(unsigned long long x) { return ull(x); }

template <class T> vector<T> make_mdvector(int n, T t) {
  return vector<T>(n, t);
}
template <class... Ts> auto make_mdvector(int n, Ts... ts) {
  return vector<decltype(make_mdvector(ts...))>(n, make_mdvector(ts...));
}

inline ll bit(int x) { return 1ll << x; }

template <class T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &&x : v) {
    is >> x;
  }
  return is;
}

template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (auto &&x : v) {
    os << x << ' ';
  }
  cout << endl;
  return os;
}
} // namespace utils
using namespace utils;

class solver {
  istream &is;
  ostream &os;

public:
  solver(istream &I, ostream &O) : is(I), os(O) {}
  ll N, M;
  vector<vector<int>> in, out;
  void run();
};

int main(int argc, char *argv[]) {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << setprecision(16) << scientific;
#ifdef XELMH
  string test_cases = "test_F.txt";
  cerr << test_cases << " -->" << endl;
  auto fs = fstream(test_cases, fstream::in);
  int loop = 0;
  while (fs) {
    loop++;
    cout << '#' << loop << "#------\n";
    solver(fs, cout).run();
  }
  if (loop <= 1) {
    cout << "===" << endl;
    while (cin)
      solver(cin, cout).run();
  }
#else
  solver(cin, cout).run();
#endif
  return 0;
}

void solver::run() {
  is >> N >> M;
  if (!is)
    return;
  out.resize(N);
  for (int ii = 0; ii < M; ++ii) {
    int s, t;
    is >> s >> t;
    s--;
    t--;
    out[s].push_back(t);
  } // end ii

  double ans = INF;
  for (int i = 0; i < N; ++i) {
    auto dp = make_mdvector(N, 1e+9);
    dp[N - 1] = 0;
    dp[N - 1] = 0;
    for (int v = N - 2; v >= 0; --v) {
      vector<double> es0;
      double mxe = 0;
      for (auto &&u : out[v]) {
        es0.push_back(dp[u] + 1);
        up_max(mxe, dp[u] + 1);
      } // end u
      if (es0.empty())
        continue;
      sort(ALL(es0));
      dp[v] = 0;
      for (int t = 0; t < es0.size(); ++t) {
        dp[v] += (es0[t]);
      } // end t
      if (i == v and es0.size() > 1) {
        dp[v] -= mxe;
        dp[v] /= es0.size() - 1;
      } else
        dp[v] /= es0.size();
    } // end v
    up_min(ans, dp[0]);
  } // end i

  os << ans << endl;
}


Fixed submission:
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdint>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <regex>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;
using ll = long long;
using ull = unsigned long long;

constexpr ll INF = 1'000'000'000'000'000'000;
namespace utils {
#define ALL(x) begin(x), end(x)
#define RALL(x) rbegin(x), rend(x)
template <class T, class Compare>
using p_queue = priority_queue<T, vector<T>, Compare>;
template <class T> using min_queue = p_queue<T, greater<T>>;
template <class T> using max_queue = p_queue<T, less<T>>;

template <class T> bool up_min(T &X, const T &A) {
  if (X > A) {
    X = A;
    return true;
  }
  return false;
}
template <class T> bool up_max(T &X, const T &A) {
  if (X < A) {
    X = A;
    return true;
  }
  return false;
}

ll operator"" _64(unsigned long long x) { return ll(x); }
ull operator"" _64u(unsigned long long x) { return ull(x); }

template <class T> vector<T> make_mdvector(int n, T t) {
  return vector<T>(n, t);
}
template <class... Ts> auto make_mdvector(int n, Ts... ts) {
  return vector<decltype(make_mdvector(ts...))>(n, make_mdvector(ts...));
}

inline ll bit(int x) { return 1ll << x; }

template <class T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &&x : v) {
    is >> x;
  }
  return is;
}

template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (auto &&x : v) {
    os << x << ' ';
  }
  cout << endl;
  return os;
}
} // namespace utils
using namespace utils;

class solver {
  istream &is;
  ostream &os;

public:
  solver(istream &I, ostream &O) : is(I), os(O) {}
  ll N, M;
  vector<vector<int>> in, out;
  void run();
};

int main(int argc, char *argv[]) {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << setprecision(16) << scientific;
#ifdef XELMH
  string test_cases = "test_F.txt";
  cerr << test_cases << " -->" << endl;
  auto fs = fstream(test_cases, fstream::in);
  int loop = 0;
  while (fs) {
    loop++;
    cout << '#' << loop << "#------\n";
    solver(fs, cout).run();
  }
  if (loop <= 1) {
    cout << "===" << endl;
    while (cin)
      solver(cin, cout).run();
  }
#else
  solver(cin, cout).run();
#endif
  return 0;
}

void solver::run() {
  is >> N >> M;
  if (!is)
    return;
  out.resize(N);
  for (int ii = 0; ii < M; ++ii) {
    int s, t;
    is >> s >> t;
    s--;
    t--;
    out[s].push_back(t);
  } // end ii

  double ans = INF;
  for (int i = 0; i < N; ++i) {
    auto dp = make_mdvector(N, 1e+9);
    dp[N - 1] = 0;
    dp[N - 1] = 0;
    for (int v = N - 2; v >= 0; --v) {
      vector<double> es0;
      double mxe = 0;
      for (auto &&u : out[v]) {
        es0.push_back(dp[u] + 1);
        up_max(mxe, dp[u] + 1);
      } // end u
      if (es0.empty())
        continue;
      dp[v] = 0;
      for (int t = 0; t < es0.size(); ++t) {
        dp[v] += (es0[t]);
      } // end t
      if (i == v and es0.size() > 1) {
        dp[v] -= mxe;
        dp[v] /= es0.size() - 1;
      } else
        dp[v] /= es0.size();
    } // end v
    up_min(ans, dp[0]);
  } // end i

  os << ans << endl;
}