loganhasson

Using the Sieve of Eratosthenes to Find Prime Numbers in Ruby

The Sieve of Eratosthenes is a super efficient way to determine whether or not numbers are prime. Essentially, it takes a max number, and via the process of elimination, gives you an array that contains every prime number up to that max number.

The very short explanation is this:

1. Create an array from 0..max
2. Starting at 2, delete every multiple of 2 from the array.
3. Then, go back to the beginning, and delete every multiple of 3.
4. Repeat this starting from the next available number at the beginning of the array.

mxriverlynn

module Capybara
  class Session
    def has_image?(src)
      has_xpath?("//img[contains(@src,\"/images/#{src}\")]")
    end
  end
end