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.

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.

 

本题和之前的那道Isomorphic Strings比较类似，用hashmap来存储char-string对，代码如下：

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