String Roatation

string_rotation_1_9.py

#!/usr/bin/env python

# String Roatation
# Assume you have a method isSubstring which checks if one word is a substring of another.
# Given two strings, s1 and s2, write code to check if s2 is a rotation of s1 using only one call
# to isSubstring(e.g., "waterbottle" is a rotation of "erbottlewat")

class StringRotation:
  def __init__(self, str_val):
    self.str_val = str_val

  def is_substring(self, sub_str):
    result = False
    starting_index = 0
    for i, c in enumerate(sub_str):
      if result and c != self.str_val[(i-starting_index)] and self.str_val[0] != c:
        result = False
      elif self.str_val[0] == c:
        starting_index = i
        result = True

    if sub_str[:(starting_index)] != self.str_val[len(self.str_val)-starting_index:]:
      result = False

    return result

if __name__ == '__main__':
  # org_str = "waterbottle"
  org_str = "waterbottleiswaterbottle"
  string_rotation = StringRotation(org_str)
  # sub_str = "erbottlewat"
  sub_str = "ottleiswaterbottlewaterb"
  print "%s is a substring of %s? : %s" % \
      (sub_str, org_str, string_rotation.is_substring(sub_str))