""" The first two consecutive numbers to have two distinct prime factors are: 14 = 2 * 7 15 = 3 * 5 The first three consecutive numbers to have three distinct prime factors are: 644 = 2^2 * 7 * 23 645 = 3 * 5 * 43 646 = 2 * 17 * 19 Find the first four consecutive integers to have four distinct prime factors each. What is the first of these numbers? """ import time from typing import Dict, List def timer(func): def wrapper(*args, **kwargs): start_time = time.time() result = func(*args, **kwargs) end_time = time.time() print(f"{func.__name__} took {end_time - start_time:.6f} seconds to run.") return result return wrapper def is_probable_prime(n: int) -> bool: """ Miller-Rabin素性测试 对于n < 3,317,044,064,679,887,385,961,981 (3e24),使用确定性基底集 """ if n < 2: return False # 小素数快速检查 small_primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37] for p in small_primes: if n % p == 0: return n == p # 写成 d * 2^s 的形式 d = n - 1 s = 0 while d % 2 == 0: d //= 2 s += 1 # 确定性基底集(对64位整数足够) # 根据研究,测试 [2, 325, 9375, 28178, 450775, 9780504, 1795265022] # 可以覆盖 < 2^64 的所有数 test_bases = [2, 325, 9375, 28178, 450775, 9780504, 1795265022] for a in test_bases: if a % n == 0: continue 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 factorize(n: int) -> Dict[int, int]: """ 优化版试除法因数分解 返回: {质因数: 指数, ...} 优化策略: 1. 快速排除小因子(2, 3) 2. 6k±1优化(跳过所有3的倍数) 3. 动态更新上界(随着因子被移除,sqrt(n)减小) 4. 对大余数进行素性预检 """ if n < 2: return {} factors = {} remaining = n # 处理负数 if remaining < 0: factors[-1] = 1 remaining = -remaining # 步骤1: 快速处理小素数(2和3) for p in [2, 3]: if remaining % p == 0: count = 0 while remaining % p == 0: remaining //= p count += 1 factors[p] = count # 步骤2: 6k±1优化 # 所有大于3的素数都形如 6k±1 # 即依次检查 5, 7, 11, 13, 17, 19... # 步长模式: +2 (到6k+1), +4 (到6k+5, 即下一个6(k+1)-1) divisor = 5 step = 2 # 交替使用 2 和 4 # 动态计算上界:只需要检查到 sqrt(remaining) # 随着remaining减小,上界也减小 while divisor * divisor <= remaining: if remaining % divisor == 0: count = 0 while remaining % divisor == 0: remaining //= divisor count += 1 factors[divisor] = count # 更新上界(优化关键!) divisor += step step = 6 - step # 2 -> 4 -> 2 -> 4... # 步骤3: 如果remaining > 1,说明remaining本身是质数 # 使用Miller-Rabin确认(对大数避免误判) if remaining > 1: # 对于小余数直接确认,大余数用素性测试 if remaining < 1_000_000 or is_probable_prime(remaining): factors[remaining] = factors.get(remaining, 0) + 1 else: # 极小概率:remaining是合数但试除法未找到因子 # 此时remaining必为两个大质数的乘积,且都 > sqrt(original_n) # 对于这种情况,可回退到Pollard's Rho(可选) factors[remaining] = 1 return factors def factorize_list(n: int) -> List[int]: """返回展开形式的质因数列表,如 12 -> [2, 2, 3]""" factors = factorize(n) result = [] for p, exp in sorted(factors.items()): result.extend([p] * exp) return result @timer def main(limit: int = 4) -> None: n = 1155 keep_ok = False res = [] while True: tl = set(factorize_list(n)) if len(tl) == limit: res.append(n) keep_ok = True if len(res) == limit and keep_ok: print(res) break else: res = [] keep_ok = False n += 1 if __name__ == "__main__": main()