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-emptyword 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.

Solution1:

思路：看起来很简单的一道题，用hashmap做就可以了。但是要注意几个cornercase，abba对应dog dog dog dog。要检查是不是

不同的字母存的string是否一样.

之前写的有点问题，用map的containsvalue来检查是不是对应。

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