FindAndReplacePattern.js

// Source : https://leetcode.com/problems/find-and-replace-pattern
// Author : Dean Shi
// Date   : 2018-08-25

/***************************************************************************************
 * You have a list of words and a pattern, and you want to know which words in words
 * matches the pattern.
 *
 * A word matches the pattern if there exists a permutation of letters p so that after
 * replacing every letter x in the pattern with p(x), we get the desired word.
 *
 * (Recall that a permutation of letters is a bijection from letters to letters: every
 * letter maps to another letter, and no two letters map to the same letter.)
 *
 * Return a list of the words in words that match the given pattern.
 *
 * You may return the answer in any order.
 *
 * Example 1:
 *
 * Input: words = ["abc","deq","mee","aqq","dkd","ccc"], pattern = "abb"
 * Output: ["mee","aqq"]
 * Explanation: "mee" matches the pattern because there is a permutation {a -> m, b ->
 * e, ...}.
 * "ccc" does not match the pattern because {a -> c, b -> c, ...} is not a permutation,
 * since a and b map to the same letter.
 *
 * Note:
 *
 * 1 <= words.length <= 50
 * 1 <= pattern.length = words[i].length <= 20
 *
 ***************************************************************************************/

/**
 * @param {string[]} words
 * @param {string} pattern
 * @return {string[]}
 */
var findAndReplacePattern = function(words, pattern) {
    return words.filter((word) => matchPattern(word, pattern))
};

function matchPattern(word, pattern) {
    const map = new Map()
    const letterInUsed = new Set()

    for (let i = 0; i < word.length; i++) {
        const hasPattern = map.has(pattern[i])
        const hasLetter = letterInUsed.has(word[i])

        if (!hasPattern && !hasLetter) {
            map.set(pattern[i], word[i])
            letterInUsed.add(word[i])
        } else if ([hasPattern, hasLetter, (map.get(pattern[i]) === word[i])].some(v => !v)) {
            return false
        }
    }
    return true
}