leetcode: 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:

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.

Java:

public class Solution {
    public boolean wordPattern(String pattern, String str) {
        String[] array = str.split(" ");
        HashMap<Character,String> hashmap = new HashMap<Character, String>();
        
        if(array.length != pattern.length()) return false;
        
        for(int i=0; i<pattern.length(); i++)
        {
            String s = hashmap.get(pattern.charAt(i));
            
            if(s!= null && !s.equals(array[i]) )
            {
                return false;
            }else if(s==null && hashmap.containsValue(array[i]))
            {
                return false;
            }else if(s == null)
            {
                hashmap.put(pattern.charAt(i),array[i]);
            }
        }
        
        return true;
    }
}