Word Pattern

Given a pattern and a string str, find if str follows the same pattern.

Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in str.

Examples: pattern = "abba", str = "dog cat cat dog" should return true. pattern = "abba", str = "dog cat cat fish" should return false. pattern = "aaaa", str = "dog cat cat dog" should return false. pattern = "abba", str = "dog dog dog dog" should return false. Notes: You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.

URL: https://leetcode.com/problems/word-pattern/

class Solution(object):
    def wordPattern(self, pattern, str):
        """
        :type pattern: str
        :type str: str
        :rtype: bool
        """
        if pattern == None or str == None:
            return False
        else:
            len_str = len(str.split(" "))
            len_pattern = len(pattern)
            if len_str != len_pattern:
                return False
            str = str.split(" ")
            lookup = {}
            for i in range(0, len(pattern)):
                s = str[i]
                p = pattern[i]
                if p in lookup:
                    if lookup[p] != s:
                        return False
                else:
                    if s in lookup.values():
                        return False
                    lookup[p] = s
            return True

if __name__ == "__main__":

    pattern = "abba"
    str = "dog cat cat dog"
    soln = Solution()
    print(soln.wordPattern(pattern, str))