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

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;
    }
}