LeetCode: Word Pattern

LeetCode: 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-empty word 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.

    Notes:

    You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.
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public class Solution {
    public boolean wordPattern(String pattern, String str) {
        if (pattern == null || str == null || pattern.isEmpty() || str.isEmpty()) {
            return false;
        }

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

        Map<Character, String> m1 = new HashMap<>();
        Map<String, Character> m2 = new HashMap<>();

        for (int i = 0; i < pattern.length(); i++) {
            char c = pattern.charAt(i);
            String s = array[i];
            if (!m1.containsKey(c) && !m2.containsKey(s)) {
                m1.put(c, s);
                m2.put(s, c);
            } else {
                 if(m1.get(c) == null||!m1.get(c).equals(s) || m2.get(s) == null ||m2.get(s) != c){
                     return false;
                 }
            }
        }
        return true;
    }
}