python中的主要因素
作者:互联网
我正在使用下面的代码寻找2500的素因子,但我的代码目前只打印2个,我不确定为什么会这样.
no = 2500
count = 0
# Finding factors of 2500
for i in range(1,no):
if no%i == 0:
# Now that the factors have been found, the prime factors will be determined
for x in range(1,no):
if i%x==0:
count = count + 1
"""Checking to see if the factor of 2500, itself only has two factor implying it is prime"""
if count == 2:
print i
谢谢
解决方法:
使用sieve of eratosthenes首先生成素数列表:
from math import sqrt
def sieve_of_eratosthenes(n):
primes = range(3, n + 1, 2) # primes above 2 must be odd so start at three and increase by 2
for base in xrange(len(primes)):
if primes[base] is None:
continue
if primes[base] >= sqrt(n): # stop at sqrt of n
break
for i in xrange(base + (base + 1) * primes[base], len(primes), primes[base]):
primes[i] = None
primes.insert(0,2)
sieve=filter(None, primes)
return sieve
def prime_factors(sieve,n):
p_f = []
for prime in sieve:
while n % prime == 0:
p_f.append(prime)
n /= prime
if n > 1:
p_f.append(n)
return p_f
sieve = sieve_of_eratosthenes(2500)
print prime_factors(sieve,2500)
标签:prime-factoring,python 来源: https://codeday.me/bug/20190928/1825203.html