Word Pattern(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:

pattern = "abba", str = "dog cat cat dog" should return true.
pattern = "abba", str = "dog cat cat fish" should return false.
pattern = "aaaa", str = "dog cat cat dog" should return false.
pattern = "abba", str = "dog dog dog dog" should return false.

Java代码

public class Solution {
    public boolean wordPattern(String pattern, String str) {
        if (pattern == null && str == null) {
            return true;
        }
        if (pattern == null || str == null) {
            return false;
        }

        char[] chars = pattern.toCharArray();
        String[] tokens = str.split(" ");
        if (tokens.length != chars.length) {
            return false;
        }

        HashMap<Character, String> map = new HashMap<Character, String>();
        HashSet<String> tokenSet = new HashSet<String>();

        for (int i = 0; i < chars.length; i++) {
            if (map.containsKey(chars[i]) && map.get(chars[i]).equals(tokens[i])) {
                continue;
            } else if (!map.containsKey(chars[i]) && !tokenSet.contains(tokens[i])) {
                map.put(chars[i], tokens[i]);
                tokenSet.add(tokens[i]);
            } else {
                return false;  
            }
        }
        return true;
    }

}

References

1. Word Pattern II