code: def lcp(s1, s2):
      '''longest common prefix
  
      >>> lcp('abcdx', 'abcdy'), lcp('', 'a'), lcp('x', 'yz')
      (4, 0, 0)
      '''
      i = 0
      for i, (c1, c2) in enumerate(zip(s1, s2)):
          if c1 != c2:
              return i
      return min(len(s1), len(s2)f lcp(s1, s2):
      '''longest common prefix
  
      >>> lcp('abcdx', 'abcdy'), lcp('', 'a'), lcp('x', 'yz')
      (4, 0, 0)
      '''
      i = 0
      for i, (c1, c2) in enumerate(zip(s1, s2)):
          if c1 != c2:
              return i
      return min(len(s1), len(s2))
docs: longest common prefix
  
      >>> lcp('abcdx', 'abcdy'), lcp('', 'a'), lcp('x', 'yz')
      (4, 0, 0)