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290. Word Pattern.js
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290. Word Pattern.js
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/*
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.
*/
/**
* @param {string} pattern
* @param {string} s
* @return {boolean}
*/
var wordPattern = function(pattern, s) {
// map char to word
let wordToChar = Object.create(null);
let charToWords = Object.create(null);
let words = s?.split(' ') ?? [];
if (pattern?.length !== words.length) {
return false;
}
// each word gets its own char
// and each char gets own word
// but we break this loop when we get
// unmatching situiation
for (let idx in words) {
if (words[idx] in wordToChar && wordToChar[words[idx]] !== pattern[idx]) {
return false;
}
if (pattern[idx] in charToWords && charToWords[pattern[idx]] !== words[idx]) {
return false;
}
wordToChar[words[idx]] = pattern[idx];
charToWords[pattern[idx]] = words[idx];
}
return true;
};