# 290. Word Pattern

[Link](https://leetcode.com/problems/word-pattern/description/)

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 that may be separated by a single space.

**Solution**

此題透過Map push function的特性，若之前key值存在就傳回上次的value。的特性來解決。

```
public boolean wordPattern(String pattern, String str) {
        Map map = new HashMap<>();
        String[] strings = str.split(" ");
        if(strings.length != pattern.length()){
            return false;
        }
        for(int i = 0; i < pattern.length(); i++){
            if(!Objects.equals(
                map.put(strings[i], i), map.put(pattern.charAt(i), i))){
                return false;
            }
        }
        return true;
    }
```
