290. Word Pattern

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Total Accepted: 27238
Total Submissions: 96500
Difficulty: Easy

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.

Java:

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public class Solution {
    public boolean wordPattern(String pattern, String str) {
        int len = pattern.length();
        String[] strs = str.split(" ");
        int size = strs.length;
        if (len != size)
            return false;
        String[] map = new String[26];
        HashSet<String> set = new HashSet<String>();
        for (int i = 0; i < len; ++i) {
            int idx = pattern.charAt(i) - 'a';
            String s = strs[i];
            if (map[idx] == null) {
                if (set.contains(s))
                    return false;
                map[idx] = s;
                set.add(s);
            } else if (!map[idx].equals(s))
                return false;
        }
        return true;
    }
}

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