Java [Leetcode 290]Word Pattern

タイトルの説明:
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.
問題解決の考え方:
HashMapを使って作ります.
コードは次のとおりです.

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