Question

我想找到600851475143的最大素因子。

但我的代码中的range不适用于600851475143，数字太大。

我该怎么办？还有更有效的算法吗？

list=[]
for i in range(1,600851475144):
    count = 0
    if 600851475143 % i == 0:
        for x in range(2,i):
            if i % x == 0:
                count+=1
                print(count)
        if count == 0:
            list.append(i)
        count=0
print(list)

Answer 1

这样做：

def PrimeFactor(n):
    m = n
    while n%2==0:
        n = n//2
    if n == 1:         # check if only 2 is largest Prime Factor 
        return 2
    i = 3
    sqrt = int(m**(0.5))  # loop till square root of number
    last = 0              # to store last prime Factor i.e. Largest Prime Factor
    while i <= sqrt :
        while n%i == 0:   
            n = n//i       # reduce the number by dividing it by it's Prime Factor
            last = i
        i+=2
    if n> last:            # the remaining number(n) is also Factor of number 
        return n
    else:
        return last
print(PrimeFactor(int(input())))

如何在python上获得大数的主要因素？

1 个答案: