## 290. Word Pattern

### Question
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.

```
Example 1:

Input: pattern = "abba", str = "dog cat cat dog"
Output: true

Example 2:

Input:pattern = "abba", str = "dog cat cat fish"
Output: false

Example 3:

Input: pattern = "aaaa", str = "dog cat cat dog"
Output: false

Example 4:

Input: pattern = "abba", str = "dog dog dog dog"
Output: false

Notes:
You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.
```

### Second time:
1. The key point of this question is the reflection between key and value.
2. We need to mapping relationship is unique, so we can use HashMap, and use two methods: containsKey and containsValue.

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