Project Euler

"Without a tagline since 2010"

About this page

This is where I put my solutions (or work towards solutions) to Project Euler problems. The problems are something I do in my spare time, so this will not be frequently updated.

I tend to use python for solving these problems, because it's just so quick to write.

Project Euler

Prime numbers

For many of these problems it's useful to have a list of prime numbers. The primes below are listed are here.

The code for finding these primes is:

flags = []
limit = 1000000
for i in range(0,limit):
    flags.append(i>1)
for i in range(2,limit):
    if flags[i]==True:
        j = i
        while j<limit:
            j = j+i
            if j<limit:
                flags[j] = False
for i in range(2,limit):
    if flags[i]:
        print i
        

To read the primes into a list:

primes_file = open('../primes/primes.txt')
primes = []
for p in primes_file.read().split('\n'):
    primes.append(int(p))

Stopwatch

Just for fun I time how long my solutions take. I place the following snippets before and after the main code:

import time
time_0 = time.time()
...
time_1 = time.time()
print 'That took %.0fms'%(1000*(time_1-time_0))