test/verify/yosupo-discrete-logarithm-mod.test.cpp

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• Last update: 2025-08-16 01:23:21+09:00
• Problem: https://judge.yosupo.jp/problem/discrete_logarithm_mod

Depends on

• Mod Log(離散対数問題) (math/combinatorics/mod-log.hpp)
• template/template.hpp

Code

// competitive-verifier: PROBLEM https://judge.yosupo.jp/problem/discrete_logarithm_mod

#include "../../template/template.hpp"

#include "../../math/combinatorics/mod-log.hpp"

int main() {
  int T;
  cin >> T;
  while(T--) {
    int64_t X, Y, M;
    cin >> X >> Y >> M;
    cout << mod_log(X, Y, M) << endl;
  }
}

#line 1 "test/verify/yosupo-discrete-logarithm-mod.test.cpp"
// competitive-verifier: PROBLEM https://judge.yosupo.jp/problem/discrete_logarithm_mod

#line 1 "template/template.hpp"
#include <bits/stdc++.h>
#if __has_include(<atcoder/all>)
#include <atcoder/all>
#endif

using namespace std;

using int64 = long long;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;

template <typename T1, typename T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& p) {
  os << p.first << " " << p.second;
  return os;
}

template <typename T1, typename T2>
istream& operator>>(istream& is, pair<T1, T2>& p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template <typename T>
istream& operator>>(istream& is, vector<T>& v) {
  for (T& in : v) is >> in;
  return is;
}

template <typename T1, typename T2>
inline bool chmax(T1& a, T2 b) {
  return a < b && (a = b, true);
}

template <typename T1, typename T2>
inline bool chmin(T1& a, T2 b) {
  return a > b && (a = b, true);
}

template <typename T = int64>
vector<T> make_v(size_t a) {
  return vector<T>(a);
}

template <typename T, typename... Ts>
auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

template <typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type fill_v(T& t, const V& v) {
  t = v;
}

template <typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type fill_v(T& t, const V& v) {
  for (auto& e : t) fill_v(e, v);
}

template <typename F>
struct FixPoint : F {
  explicit FixPoint(F&& f) : F(std::forward<F>(f)) {}

  template <typename... Args>
  decltype(auto) operator()(Args&&... args) const {
    return F::operator()(*this, std::forward<Args>(args)...);
  }
};

template <typename F>
inline decltype(auto) MFP(F&& f) {
  return FixPoint<F>{std::forward<F>(f)};
}
#line 4 "test/verify/yosupo-discrete-logarithm-mod.test.cpp"

#line 1 "math/combinatorics/mod-log.hpp"
/**
 * @brief Mod Log(離散対数問題)
 *
 */
int64_t mod_log(int64_t a, int64_t b, int64_t p) {
  int64_t g = 1;

  for (int64_t i = p; i; i /= 2) (g *= a) %= p;
  g = __gcd(g, p);

  int64_t t = 1, c = 0;
  for (; t % g; c++) {
    if (t == b) return c;
    (t *= a) %= p;
  }
  if (b % g) return -1;

  t /= g;
  b /= g;

  int64_t n = p / g, h = 0, gs = 1;

  for (; h * h < n; h++) (gs *= a) %= n;

  unordered_map<int64_t, int64_t> bs;
  for (int64_t s = 0, e = b; s < h; bs[e] = ++s) {
    (e *= a) %= n;
  }

  for (int64_t s = 0, e = t; s < n;) {
    (e *= gs) %= n;
    s += h;
    if (bs.count(e)) return c + s - bs[e];
  }
  return -1;
}
#line 6 "test/verify/yosupo-discrete-logarithm-mod.test.cpp"

int main() {
  int T;
  cin >> T;
  while(T--) {
    int64_t X, Y, M;
    cin >> X >> Y >> M;
    cout << mod_log(X, Y, M) << endl;
  }
}

Test cases

Env	Name	Status	Elapsed	Memory
g++	even_mod_00	AC	145 ms	5 MB
g++	even_mod_01	AC	182 ms	5 MB
g++	even_mod_impossible_00	AC	5 ms	4 MB
g++	even_mod_impossible_01	AC	5 ms	4 MB
g++	example_00	AC	5 ms	4 MB
g++	max_random_00	AC	225 ms	5 MB
g++	max_random_01	AC	214 ms	5 MB
g++	max_random_02	AC	189 ms	5 MB
g++	max_random_yes_00	AC	213 ms	5 MB
g++	max_random_yes_01	AC	218 ms	5 MB
g++	max_random_yes_prime_00	AC	294 ms	5 MB
g++	max_random_yes_prime_01	AC	301 ms	5 MB
g++	random_00	AC	67 ms	5 MB
g++	random_01	AC	109 ms	5 MB
g++	random_02	AC	145 ms	5 MB
g++	random_prime_00	AC	324 ms	5 MB
g++	random_prime_01	AC	315 ms	5 MB
g++	small_00	AC	5 ms	4 MB
g++	small_01	AC	5 ms	4 MB
g++	small_02	AC	5 ms	4 MB
clang++	even_mod_00	AC	145 ms	5 MB
clang++	even_mod_01	AC	182 ms	5 MB
clang++	even_mod_impossible_00	AC	6 ms	4 MB
clang++	even_mod_impossible_01	AC	5 ms	4 MB
clang++	example_00	AC	5 ms	4 MB
clang++	max_random_00	AC	224 ms	5 MB
clang++	max_random_01	AC	212 ms	5 MB
clang++	max_random_02	AC	187 ms	5 MB
clang++	max_random_yes_00	AC	214 ms	5 MB
clang++	max_random_yes_01	AC	216 ms	5 MB
clang++	max_random_yes_prime_00	AC	291 ms	5 MB
clang++	max_random_yes_prime_01	AC	302 ms	5 MB
clang++	random_00	AC	67 ms	5 MB
clang++	random_01	AC	108 ms	5 MB
clang++	random_02	AC	145 ms	5 MB
clang++	random_prime_00	AC	321 ms	5 MB
clang++	random_prime_01	AC	313 ms	5 MB
clang++	small_00	AC	5 ms	4 MB
clang++	small_01	AC	5 ms	4 MB
clang++	small_02	AC	5 ms	4 MB

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