290. Word Pattern

Problem

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.

Solution

/**
 * @param {string} pattern
 * @param {string} s
 * @return {boolean}
 */
var wordPattern = function(pattern, s) {
    var map = {};
    var used = new Map();
    var words = s.split(' ');
    if (pattern.length !== words.length) return false;
    for (var i = 0; i < pattern.length; i++) {
        if (!map[pattern[i]]) {
            if (used.has(words[i])) return false;
            used.set(words[i], true);
            map[pattern[i]] = words[i];
        } else if (map[pattern[i]] !== words[i]) {
            return false;
        }
    }
    return true;
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).