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290. Word Pattern

Hash Table String

Problem - Word Pattern

Easy

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. Specifically:

  • Each letter in pattern maps to exactly one unique word in s.
  • Each unique word in s maps to exactly one letter in pattern.
  • No two letters map to the same word, and no two words map to the same letter.

 

Example 1:

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

Output: true

Explanation:

The bijection can be established as:

  • 'a' maps to "dog".
  • 'b' maps to "cat".

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.

Solutions

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class Solution:
    def wordPattern(self, pattern: str, s: str) -> bool:
        words = s.split()
        if len(pattern) != len(words):
            return False

        hash_table1 = {}
        hash_table2 = {}
        for val1, val2 in zip(pattern, words):
            if (val1 in hash_table1 and hash_table1[val1] != val2) or (val2 in hash_table2 and hash_table2[val2] != val1):
                return False
            hash_table1[val1] = val2
            hash_table2[val2] = val1

        return True

Submission Stats:

  • Runtime: 0 ms (100.00%)
  • Memory: 17.9 MB (36.19%)