Question

If I have a string such as ‘abcde’ and I want to get a 2d array of all combinations of 1 or 2 letters.

[ ['a', 'b', 'c', 'd', 'e'], ['ab', 'c', 'de'], ['a', 'bc', 'd', 'e'] ...

How would I go abouts doing so?

I want to do this in ruby, and think I should be using a regex. I’ve tried using

strn = 'abcde'
strn.scan(/[a-z][a-z]/)

but this is only going to give me the distinct sets of 2 characters

['ab', 'cd']

Answer 1

I think this should do it (haven’t tested yet):

def find_letter_combinations(str)
  return [[]] if str.empty?
  combinations = []
  find_letter_combinations(str[1..-1]).each do |c|
    combinations << c.unshift(str[0])
  end
  return combinations if str.length == 1
  find_letter_combinations(str[2..-1]).each do |c|
    combinations << c.unshift(str[0..1])
  end
  combinations
end