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290. Word Pattern

Difficulty Topics

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.

 

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

word-pattern.py
class Solution:
    def wordPattern(self, pattern: str, s: str) -> bool:
        def f(s):
            seen = {}
            res = []

            for x in s:
                if x not in seen:
                    seen[x] = len(seen)

                res.append(seen[x])

            return "".join(map(str, res))

        return f(pattern) == f(s.split())