substringmatch.rb

=begin
STRING SEARCHING
CHALLENGE DESCRIPTION:
You are given two strings. Determine if the second string is a substring of the
first (Do NOT use any substr type library function). The second string may
contain an asterisk(*) which should be treated as a regular expression i.e.
matches zero or more characters. The asterisk can be escaped by a \ char in
which case it should be interpreted as a regular '*' character. To summarize:
the strings can contain alphabets, numbers, * and \ characters.
INPUT SAMPLE:
Your program should accept as its first argument a path to a filename. The
input file contains two comma delimited strings per line. E.g.
Hello,ell
This is good, is
CodeEval,C*Eval
Old,Young
OUTPUT SAMPLE:
If the second string is indeed a substring of the first, print out a 'true'
(lowercase), else print out a 'false'(lowercase), one per line. E.g.
true
true
true
false
=end

lines = File.readlines(ARGV[0])

lines.each do |line|
  strings = line.split(",")
  first = strings.first
  second = strings.last.chomp
  this_word = ""
  result = true
  while second.length > 0
    this_char = second.chars.shift
    second = second[1..-1]
    if this_char == "*"
      if !first.include?(this_word)
        result = false
      else
        first = first[this_word.length..-1]
        this_word = ""
      end
    elsif this_char == "\\"
      if second.chars.shift == "*"
        this_word << "*"
        second = second[1..-1]
      else
        this_word << this_char
      end
    else
      this_word << this_char
    end
  end
  if !result
    puts false
  else
    puts first.include?(this_word)
  end
end