Problem #290: Word Pattern

Intuition & Strategy Breakdown

Use two hash maps for bi-directional mapping between pattern characters and words in s.

Python Solution

class Solution:
    def wordPattern(self, pattern: str, s: str) -> bool:
        words = s.split()
        if len(pattern) != len(words):
            return False
        
        char_to_word = {}
        word_to_char = {}
        
        for char, word in zip(pattern, words):
            if char in char_to_word and char_to_word[char] != word:
                return False
            if word in word_to_char and word_to_char[word] != char:
                return False
            
            char_to_word[char] = word
            word_to_char[word] = char
            
        return True

Java Solution

class Solution {
    public boolean wordPattern(String pattern, String s) {
        String[] words = s.split(" ");
        if (words.length != pattern.length()) {
            return false;
        }

        Map charToWord = new HashMap<>();
        Map wordToChar = new HashMap<>();

        for (int i = 0; i < pattern.length(); i++) {
            char c = pattern.charAt(i);
            String w = words[i];

            if (charToWord.containsKey(c) && !charToWord.get(c).equals(w)) {
                return false;
            }
            if (wordToChar.containsKey(w) && wordToChar.get(w) != c) {
                return false;
            }

            charToWord.put(c, w);
            wordToChar.put(w, c);
        }

        return true;
    }
}