Problem of the Day
A new programming or logic puzzle every Mon-Fri

That title sounds daunting. Fear not! Our regex parser will be quite simple. We'll be creating a function that tags in pattern and a string to match against. The parser only needs to recognize one special character, *. If the pattern matches against the string return true, else false. Here are some example inputs/outputs:

parse('abc', 'abc')
> true

parse('a*bc', 'abc')
> true

parse('*ca', 'cba')
> false

parse('c*a', 'cccca')
> true

As a quick refresher, the * character matches zero or more occurrences of the preceding character in a row.

Comments:

• Nick Krichevsky - 10 years, 7 months ago

  Pretty sure I got it, I met all the requirements above, so I think I got it, but ... http://xkcd.com/1171/

  s = "ccccccca"
  p = "*ca"
  
  def stargex(string,pattern):
      if '*' in pattern:
          pattern = pattern.replace('*','')
          if pattern in string:
              return True
          else:
              return False
      else:
          if pattern == string:
              return True
          else:
              return False
  print stargex(s,p)  
  

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• Pericolo - 10 years, 7 months ago

  I guess your code gives the wrong output for inputs such as: s = "cccab", p = "*ca"

  A simple "if pattern in string" after removing the '*' from the pattern just won't do. It takes more than that.

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• Nick Krichevsky - 10 years, 7 months ago

  Damn you're right. I'll go rethink this.

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• Max Burstein - 10 years, 7 months ago

  lol I love that xkcd.

  On another note after checking your code I realize I made a mistake on the last sample output. It originally said *ca for the pattern. However, that has no preceding characters so it's an invalid regex so I changed it to c*a which matches what I was going for there.

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