Snippet

project_euler/3.rb

Code:

# Project Euler Problem 3: Largest Prime Factor

# https://projecteuler.net/problem=3

# The prime factors of 13195 are 5, 7, 13 and 29.
# What is the largest prime factor of the number 600851475143?

def prime_factors(n)
    (2...n).each do |factor|
        if (n % factor == 0) 
            other_factor = n / factor
            return [*prime_factors(factor), *prime_factors(other_factor)]
        end
    end
    return [n]
end

puts prime_factors(13195).max
puts prime_factors(600851475143).max

Output:

29
6857