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# 0290. Word Pattern

<https://leetcode.com/problems/word-pattern>

## Description

Given a `pattern` and a string `s`, find if `s` 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 `s`.

**Example 1:**

```
**Input:** pattern = "abba", s = "dog cat cat dog"
**Output:** true
```

**Example 2:**

```
**Input:** pattern = "abba", s = "dog cat cat fish"
**Output:** false
```

**Example 3:**

```
**Input:** pattern = "aaaa", s = "dog cat cat dog"
**Output:** false
```

**Example 4:**

```
**Input:** pattern = "abba", s = "dog dog dog dog"
**Output:** false
```

**Constraints:**

* `1 <= pattern.length <= 300`
* `pattern` contains only lower-case English letters.
* `1 <= s.length <= 3000`
* `s` contains only lower-case English letters and spaces `' '`.
* `s` **does not contain** any leading or trailing spaces.
* All the words in `s` are separated by a **single space**.

## ac

```java
class Solution {
    public boolean wordPattern(String pattern, String str) {
        // edge cases
        if (str.length() < pattern.length()) return false;

        String[] words = str.split(" ");
        if (pattern.length() != words.length) return false;

        Map<Character, String> map = new HashMap<>();
        Set<String> set = new HashSet<>();

        for (int i = 0; i < pattern.length(); i++) {
            char c = pattern.charAt(i);
            if (map.containsKey(c)) {
                if (!words[i].equals(map.get(c))) return false;
            } else {
                if (set.contains(words[i])) return false;
                map.put(c, words[i]);
            }
            set.add(words[i]);
        }

        return true;
    }
}
```