tests/Discrete_Logarithm.test.cpp

View this file on GitHub
Last update: 2025-11-28 02:09:51+07:00
Problem: https://judge.yosupo.jp/problem/discrete_logarithm_mod

Depends on

Code

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

#include "../misc/macros.h"
#include "../math/ModLog.h"

void solve() {
  i64 a, b, m;
  cin >> a >> b >> m;
  if (m == 1 || b == 1) {  // because of the bs nonnegative and 0^0 = 1
    cout << 0 << '\n';
    return;
  }
  cout << modLog(a, b, m) << '\n';
}

int main() {
  cin.tie(0)->sync_with_stdio(0);
  cin.exceptions(cin.failbit);
  int tc = 1;
  cin >> tc;
  for (int i = 1; i <= tc; ++i) {
    solve();
  }
}

#line 1 "tests/Discrete_Logarithm.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/discrete_logarithm_mod"

#line 1 "misc/macros.h"
// #pragma GCC optimize("Ofast,unroll-loops")       // unroll long, simple loops
// #pragma GCC target("avx2,fma")                   // vectorizing code
// #pragma GCC target("lzcnt,popcnt,abm,bmi,bmi2")  // for fast bitset operation

#include <bits/extc++.h>
#include <tr2/dynamic_bitset>

using namespace std;
using namespace __gnu_pbds;  // ordered_set, gp_hash_table
// using namespace __gnu_cxx; // rope

// for templates to work
#define all(x) (x).begin(), (x).end()
#define sz(x) (int) (x).size()
#define pb push_back
#define eb emplace_back
using i32 = int32_t;
using u32 = uint32_t;
using i64 = int64_t;
using u64 = uint64_t;
using i128 = __int128_t;
using u128 = __uint128_t;
using ld = long double;
using pii = pair<i32, i32>;
using vi = vector<i32>;

// fast map
const int RANDOM = chrono::high_resolution_clock::now().time_since_epoch().count();
struct chash {  // customize hash function for gp_hash_table
  int operator()(int x) const { return x ^ RANDOM; }
};
gp_hash_table<int, int, chash> table;

/* ordered set
    find_by_order(k): returns an iterator to the k-th element (0-based)
    order_of_key(k): returns the number of elements in the set that are strictly less than k
*/
template <class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

/*  rope
    rope <int> cur = v.substr(l, r - l + 1);
    v.erase(l, r - l + 1);
    v.insert(v.mutable_begin(), cur);
*/
#line 1 "math/ModLog.h"
i64 modLog(i64 a, i64 b, i64 m) {
  i64 n = (i64) sqrt(m) + 1, e = 1, f = 1, j = 1;
  unordered_map<i64, i64> A;
  while (j <= n && (e = f = e * a % m) != b % m) A[e * b % m] = j++;
  if (e == b % m) return j;
  if (gcd(m, e) == gcd(m, b)) {
    for (int i = 2; i < n + 2; ++i) {
      if (A.count(e = e * f % m)) return n * i - A[e];
    }
  }
  return -1;
}
#line 5 "tests/Discrete_Logarithm.test.cpp"

void solve() {
  i64 a, b, m;
  cin >> a >> b >> m;
  if (m == 1 || b == 1) {  // because of the bs nonnegative and 0^0 = 1
    cout << 0 << '\n';
    return;
  }
  cout << modLog(a, b, m) << '\n';
}

int main() {
  cin.tie(0)->sync_with_stdio(0);
  cin.exceptions(cin.failbit);
  int tc = 1;
  cin >> tc;
  for (int i = 1; i <= tc; ++i) {
    solve();
  }
}