Python Data Structures and Algorithms Tutorial

Word Pattern LeetCode Solution

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Given a pattern and a string s, find if s 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 s.

Example 1:

Input: pattern = "abba", s = "dog cat cat dog"
Output: true

Example 2:

Input: pattern = "abba", s = "dog cat cat fish"
Output: false

Example 3:

Input: pattern = "aaaa", s = "dog cat cat dog"
Output: false

Constraints:

1 <= pattern.length <= 300
pattern contains only lower-case English letters.
1 <= s.length <= 3000
s contains only lowercase English letters and spaces ' '.
s does not contain any leading or trailing spaces.
All the words in s are separated by a single space.

Solution:

class Solution(object):
    def wordPattern(self, pattern, s):
        """
        :type pattern: str
        :type s: str
        :rtype: bool
        """
        words = s.split()
        if len(pattern) != len(words):
            return False

        pattern_dict = {}
        word_dict = {}

        for p, w in zip(pattern, words):
            if p not in pattern_dict:
                pattern_dict[p] = w
            if w not in word_dict:
                word_dict[w] = p
            if pattern_dict[p] != w or word_dict[w] != p:
                return False

        return True

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