Find the longest common starting substring in a set of strings [closed]

Answer 1

Here's a solution using regular expressions in Ruby:

def build_regex(string)
  arr = []
  arr << string.dup while string.chop!
  Regexp.new("^(#{arr.join("|")})")
end

def substring(first, *strings)
  strings.inject(first) do |accum, string|
    build_regex(accum).match(string)[0]
  end
end