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.

Example 1:

Input: pattern = "abba", str = "dog cat cat dog"
Output: true

Example 2:

Input:pattern = "abba", str = "dog cat cat fish"
Output: false

Example 3:

Input: pattern = "aaaa", str = "dog cat cat dog"
Output: false

Example 4:

Input: pattern = "abba", str = "dog dog dog dog"
Output: false

Notes:
You may assume pattern contains only lowercase letters, and str contains lowercase letters that may be separated by a single space.

time = O(n), space = O(n)

class Solution {
    public boolean wordPattern(String pattern, String str) {
        String[] words = str.split(" ");
        if(pattern.length() != words.length) {
            return false;
        }
        
        Map<Character, String> map = new HashMap<>();
        Set<String> set = new HashSet<>();
        
        for(int i = 0; i < words.length; i++) {
            char c = pattern.charAt(i);
            if(!map.containsKey(c)) {
                if(set.contains(words[i])) {
                    return false;
                }
                map.put(c, words[i]);
                set.add(words[i]);
            } else {
                if(!map.get(c).equals(words[i])) {
                    return false;
                }
            }
        }
        
        return true;
    }
}