0290-word-pattern

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Description

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.

Solution(Python)

class Solution:
    def wordPattern(self, pattern: str, s: str) -> bool:
        return self.transformarr(pattern) == self.transformarr(s.split()) 
    def transformarr(self, arr) -> str:
        index_mapping = {}
        new_str = []

        for i, c in enumerate(arr):
            if c not in index_mapping:
                index_mapping[c] = hash(i)
            new_str.append(str(index_mapping[c]))

        return " ".join(new_str)

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