五分钟捡起Python妥妥的

import math

def primeFactor(source):
    start = int(math.floor(math.sqrt(source)))
    
    while start > 1:
        print start
        mod = source % start
        if mod == 0 and isPrime(start):
            return start
        start -= 1
        
def isPrime(source):
    start = source / 2
    
    while start > 1:
        if source % start == 0:
            return False
        start -= 1
        
    return True
        
    
print primeFactor(600851475143)

import java.math.BigInteger;

public class test {
    public static void main(String[] args) {
        System.out.println(primeFactor("600851475143"));
    }
    
    public static long primeFactor(String source) {
        BigInteger src = new BigInteger(source);
        long start = (long) src.divide(new BigInteger("2")).longValue();
        
        for (long number = start; number > 0; number--) {
            System.out.println(number);
            long module = src.mod(BigInteger.valueOf(number)).longValue();
            if (module == 0 && isPrime(number))
                return number;
        }
        
        return -1;
    }
    
    public static boolean isPrime(long source) {
        long start = (long) Math.floor(source / 2);
        
        for (long number = start; number > 1; number--) {
            long module = source % number;
            if (module == 0)
                return false;
        }
        return true;
    }
}

前边的一分钟查忘记的语法，四分钟写代码，十秒出答案。

后边的写了一个多小时现在还在算。谁告诉我BigInteger怎么开房不开方。