wordPattern.js

/*
Given a pattern and a string str, find if str 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 str.

Examples:
pattern = "abba", str = "dog cat cat dog" should return true.
pattern = "abba", str = "dog cat cat fish" should return false.
pattern = "aaaa", str = "dog cat cat dog" should return false.
pattern = "abba", str = "dog dog dog dog" should return false.
Notes:
You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.

Credits:
Special thanks to @minglotus6 for adding this problem and creating all test cases.
*/
/**
 * @param {string} pattern
 * @param {string} str
 * @return {boolean}
 */
var wordPattern = function(pattern, str) {
    const patternArray = pattern.split('');
    const candidate = str.split(' ');
    const hash = {};
    const reverseHash = {};

    if(patternArray.length!==candidate.length){
        return false;
    }
    for(let i=0; i<candidate.length; i++){
        if(!hash[patternArray[i]] && !reverseHash[candidate[i]] ){
            hash[patternArray[i]] = candidate[i];
            reverseHash[candidate[i]] = patternArray[i];
        } else {
            if( hash[patternArray[i]] !== candidate[i] || reverseHash[candidate[i]] !== patternArray[i]){
                return false;
            }
        }
    }
    return true;
};