Word Pattern

题目
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.

答案

class Solution {
    public boolean wordPattern(String pattern, String str) {
        String[] words = str.split(" ");
        if(words.length != pattern.length()) return false;
        Map map = new HashMap<>();
        Map map2 = new HashMap<>();

        for(int i = 0; i < pattern.length(); i++) {
            char p = pattern.charAt(i);
            String w = map.get(p);
            if(w == null) {
                if(map2.get(words[i]) != null) return false;
                map.put(p, words[i]);
                map2.put(words[i], p);
            }
            else {
                if(!w.equals(words[i])) return false;
            }
        }
        return true;
    }
}