290. Word Pattern java solutions

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:

1. pattern = "abba", str = "dog cat cat dog" should return true.
2. pattern = "abba", str = "dog cat cat fish" should return false.
3. pattern = "aaaa", str = "dog cat cat dog" should return false.
4. 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.

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