| 1 | #include "mod_pow.cpp" |
| 2 | bool is_probable_prime(ll n, int k) { |
| 3 | if (~n & 1) return n == 2; |
| 4 | if (n <= 3) return n == 3; |
| 5 | int s = 0; ll d = n - 1; |
| 6 | while (~d & 1) d >>= 1, s++; |
| 7 | while (k--) { |
| 8 | ll a = uniform_int_distribution(2LL, n-2)(rng); |
| 9 | ll x = mod_pow(a, d, n); |
| 10 | if (x == 1 || x == n - 1) continue; |
| 11 | bool ok = false; |
| 12 | rep(i,0,s-1) { |
| 13 | x = (x * x) % n; |
| 14 | if (x == 1) return false; |
| 15 | if (x == n - 1) { ok = true; break; } |
| 16 | } |
| 17 | if (!ok) return false; |
| 18 | } return true; } |
| 19 | // vim: cc=60 ts=2 sts=2 sw=2: |