Snippet

project_euler/10.rb

Code:

# Project Euler Problem 10: Summation of Primes

# https://projecteuler.net/problem=10

# The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
# Find the sum of all the primes below two million.

def sieve(max)
    primes = (0..max).to_a
    primes[0] = primes[1] = nil
    counter = 0
    primes.each do |prime|
        next unless prime 
        break if prime ** 2 > max
        counter += 1
        (prime ** 2).step(max, prime) { |m| primes[m] = nil }
    end
    return primes.compact
end


def solve(n)
    return sieve(n).sum
end

puts solve(10)
puts solve(2_000_000)

Output:

17
142913828922