0x0003 - Project Euler 003

Fri, 28 Oct 2011 21:06:30 +0000

Problem:

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?

Solution:

A neat little trick for Linux/UNIX users in Python is:


from commands import *
print int(getoutput("factor 600851475143").split()[::-1][0])

But a general program could be:


p, n = 2, 600851475143

while (p*p <= n) :
 if (n % p == 0) :
 n /= p
 if p == 2: p += 1
 else: p += 2

print n

Analysis:

I have solved this problem in two ways using Python 2.7 in Ubuntu 10.10. In the first code, initially I’ve imported all methods from the ‘commands’ module in Python, using which I can run Operating System(OS) commands and get the result from within my Python program. The next line is where the “cheat” lies.

Linux on Rohit Jha

0x0003 - Project Euler 003