290_Word_Pattern.js

// LeetCode 290. Word Pattern

// 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.

function wordPattern(pattern, str) {
    var patternMap = {};
    var strMap = {};
    var ary = str.split(/\s/);

    if ((pattern.length != str.split(/\s/).length)) {
        return false;
    }

    for (var i in pattern) {
        var p = pattern[i];
        var s = ary[i];
        if (!patternMap[p]) {
            patternMap[p] = s;
        } else if (patternMap[p] != s) {
            return false;
        }
        if (!strMap[s]) {
            strMap[s] = p;
        } else if (strMap[s] != p) {
            return false;
        }
    }
    return true;
}

wordPattern("abba", "dog cat cat dog");