leetcode - 290. Word Pattern

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

Use hashmap to map pattern to s

Time complexity: $o(n)$
Space complexity: $o(n)$

Code

class Solution:
    def wordPattern(self, pattern: str, s: str) -> bool:
        s = s.split(' ')
        if len(pattern) != len(s) or len(set(pattern)) != len(set(s)):
            return False
        p_to_s = {}
        for each_p, each_s in zip(pattern, s):
            if each_p not in p_to_s:
                p_to_s[each_p] = each_s
            elif p_to_s[each_p] != each_s:
                return False
        return True