kyopro-lib

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:x: test/yosupo-judge/discrete_logarithm_mod/main.test.cpp

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Code

#define PROBLEM "https://judge.yosupo.jp/problem/discrete_logarithm_mod"

#include <iostream>
#include "Mylib/IO/input_tuples.cpp"
#include "Mylib/Number/Mod/mod_log.cpp"

namespace hl = haar_lib;

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

  int T;
  std::cin >> T;

  for (auto [X, Y, M] : hl::input_tuples<int, int, int>(T)) {
    std::cout << hl::mod_log(X, Y, M).value_or(-1) << "\n";
  }

  return 0;
}
#line 1 "test/yosupo-judge/discrete_logarithm_mod/main.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/discrete_logarithm_mod"

#include <iostream>
#line 2 "Mylib/IO/input_tuples.cpp"
#include <initializer_list>
#line 4 "Mylib/IO/input_tuples.cpp"
#include <tuple>
#include <utility>
#include <vector>
#line 6 "Mylib/IO/input_tuple.cpp"

namespace haar_lib {
  template <typename T, size_t... I>
  static void input_tuple_helper(std::istream &s, T &val, std::index_sequence<I...>) {
    (void) std::initializer_list<int>{(void(s >> std::get<I>(val)), 0)...};
  }

  template <typename T, typename U>
  std::istream &operator>>(std::istream &s, std::pair<T, U> &value) {
    s >> value.first >> value.second;
    return s;
  }

  template <typename... Args>
  std::istream &operator>>(std::istream &s, std::tuple<Args...> &value) {
    input_tuple_helper(s, value, std::make_index_sequence<sizeof...(Args)>());
    return s;
  }
}  // namespace haar_lib
#line 8 "Mylib/IO/input_tuples.cpp"

namespace haar_lib {
  template <typename... Args>
  class InputTuples {
    struct iter {
      using value_type = std::tuple<Args...>;
      value_type value;
      bool fetched = false;
      int N, c = 0;

      value_type operator*() {
        if (not fetched) {
          std::cin >> value;
        }
        return value;
      }

      void operator++() {
        ++c;
        fetched = false;
      }

      bool operator!=(iter &) const {
        return c < N;
      }

      iter(int N) : N(N) {}
    };

    int N;

  public:
    InputTuples(int N) : N(N) {}

    iter begin() const { return iter(N); }
    iter end() const { return iter(N); }
  };

  template <typename... Args>
  auto input_tuples(int N) {
    return InputTuples<Args...>(N);
  }
}  // namespace haar_lib
#line 2 "Mylib/Number/Mod/mod_log.cpp"
#include <cmath>
#include <numeric>
#include <optional>
#include <unordered_map>
#line 2 "Mylib/Number/Mod/mod_inv.cpp"
#include <cstdint>
#line 4 "Mylib/Number/Mod/mod_inv.cpp"

namespace haar_lib {
  constexpr int64_t mod_inv(int64_t a, int64_t m) {
    int64_t b = m, u = 1, v = 0;

    while (b) {
      int64_t t = a / b;
      a -= t * b;
      a = a ^ b;
      b = a ^ b;
      a = a ^ b;

      u -= t * v;
      u = u ^ v;
      v = u ^ v;
      u = u ^ v;
    }

    u %= m;
    if (u < 0) u += m;

    return u;
  }
}  // namespace haar_lib
#line 3 "Mylib/Number/Mod/mod_pow.cpp"

namespace haar_lib {
  constexpr int64_t mod_pow(int64_t n, int64_t p, int64_t m) {
    int64_t ret = 1;
    while (p > 0) {
      if (p & 1) (ret *= n) %= m;
      (n *= n) %= m;
      p >>= 1;
    }
    return ret;
  }
}  // namespace haar_lib
#line 8 "Mylib/Number/Mod/mod_log.cpp"

namespace haar_lib {
  std::optional<int64_t> mod_log(int64_t a, int64_t b, int64_t m) {
    if (b == 1) return 0;

    int64_t d = 0;

    while (1) {
      if (auto g = std::gcd(a, m); g != 1) {
        if (b % g != 0) return {};

        d += 1;
        m /= g;
        b /= g;
        (b *= mod_inv(a / g, m)) %= m;

        if (b == 1) return d;
      } else {
        break;
      }
    }

    const int64_t sq = std::sqrt(m) + 1;

    std::unordered_map<int64_t, int64_t> mp;
    {
      int64_t t = 1 % m;

      for (int i = 0; i < sq; ++i) {
        if (mp.find(t) == mp.end()) mp[t] = i;
        (t *= a) %= m;
      }
    }

    {
      int64_t A = mod_pow(mod_inv(a, m), sq, m);
      int64_t t = b % m;

      for (int i = 0; i < sq; ++i) {
        if (mp.find(t) != mp.end()) {
          int64_t ret = i * sq + mp[t] + d;

          return ret;
        }

        (t *= A) %= m;
      }
    }

    return {};
  }
}  // namespace haar_lib
#line 6 "test/yosupo-judge/discrete_logarithm_mod/main.test.cpp"

namespace hl = haar_lib;

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

  int T;
  std::cin >> T;

  for (auto [X, Y, M] : hl::input_tuples<int, int, int>(T)) {
    std::cout << hl::mod_log(X, Y, M).value_or(-1) << "\n";
  }

  return 0;
}
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