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Question

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:

1. pattern = “abba”, str = “dog cat cat dog” should return true.
2. pattern = “abba”, str = “dog cat cat fish” should return false.
3. pattern = “aaaa”, str = “dog cat cat dog” should return false.
4. 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.

Solution

Result: Accepted Time: 40 ms

Here should be some explanations.

class Solution(object):
    def wordPattern(self, pattern, str):
        """
        :type pattern: str
        :type str: str
        :rtype: bool
        """
        words = str.split(' ')
        cnt = len(words)
        if cnt <> len(pattern):
            return False
        mp1={}
        mp2={}
        for i in xrange(cnt):
            if pattern[i] not in mp1:
                mp1[pattern[i]] = words[i]
            elif mp1[pattern[i]] <> words[i]:
                return False
            if words[i] not in mp2:
                mp2[words[i]] = pattern[i]
            elif mp2[words[i]] <> pattern[i]:
                return False
        return True
        

Complexity Analytics

• Time Complexity: $O(n)$
• Space Complexity: $O(1)$