Euler Problem 3 Python Solution
The problem is to find the largest prime factor of 600851475143.
Some ugly python and an ugly solution. Clearly not very computationally efficient as I’m recalculating primes each time. There are also other computationally more efficient solutions out there in any case. This is just here for my reference:
import math
def getprimes(input):
i = input #math.sqrt(input)
vals = range(2,int(i))
for n in vals:
for j in xrange(n+n,int(i),n):
if j in vals:
vals.remove(j)
vals.reverse()
return vals
input = 600851475143L
primes_max = 100
while 1:
primes = getprimes(primes_max)
#print primes
p = 0
for i in primes:
if input%i == 0:
print "factor: ",i
input = input/i
p = 1
if primes_max > math.sqrt(input):
if p == 0:
print "factor: ",input
break
primes_max = primes_max + 1000
print primes_max
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