"""
The prime factors of 13195 are 5, 7, 13and 29.
What is the largest prime factor of the number 600851475143 ?
"""

import random
from math import gcd
from typing import List, Set


def is_probable_prime(n: int, trials: int = 10) -> bool:
    """Miller-Rabin素性测试（快速判断是否为质数）"""
    if n < 2:
        return False
    if n in (2, 3):
        return True
    if n % 2 == 0:
        return False

    # 将 n-1 写成 d * 2^s 的形式
    d = n - 1
    s = 0
    while d % 2 == 0:
        d //= 2
        s += 1

    # 测试
    for _ in range(trials):
        a = random.randrange(2, n - 1)
        x = pow(a, d, n)
        if x == 1 or x == n - 1:
            continue
        for _ in range(s - 1):
            x = pow(x, 2, n)
            if x == n - 1:
                break
        else:
            return False
    return True


def pollards_rho(n: int, max_iter: int = 100000) -> int | None:
    """
    Pollard's Rho 算法：返回n的一个非平凡因子

    Args:
        n: 待分解的合数
        max_iter: 最大迭代次数防止无限循环

    Returns:
        n的一个因子（可能是质数也可能是合数）
        若失败返回None
    """

    if n % 2 == 0:
        return 2

    # 随机生成多项式 f(x) = x^2 + c (mod n)
    c = random.randrange(1, n - 1)

    def f(x):
        return (pow(x, 2, n) + c) % n

    # Floyd 判圈算法
    x = random.randrange(2, n - 1)
    y = x
    d = 1

    iter_count = 0
    while d == 1 and iter_count < max_iter:
        x = f(x)  # 乌龟：走一步
        y = f(f(y))  # 兔子：走两步
        d = gcd(abs(x - y), n)
        iter_count += 1

    if d == n:
        # 失败，尝试其他参数（递归或返回None）
        return pollards_rho(n, max_iter) if max_iter > 1000 else None

    return d


def factorize(n: int | None) -> List[int | None]:
    """
    完整因数分解：递归分解所有质因数

    Args:
        n: 待分解的正整数

    Returns:
        质因数列表（可能含重复）
    """
    if n == 1:
        return []
    if n is None:
        return [None]

    # 如果是质数，直接返回
    if is_probable_prime(n):
        return [n]

    # 获取一个因子
    factor = pollards_rho(n)

    if factor is None:
        return [None]

    # 递归分解
    return factorize(factor) + factorize(n // factor)


def get_prime_factors(n: int) -> Set[int | None]:
    """获取所有不重复的质因数"""
    return set(factorize(n))


if __name__ == "__main__":
    print(get_prime_factors(60))  # {2, 3, 5}