290. 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:

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.

Notes:

You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.

String类题目。

可采用hash map来解。 这里需注意的是不用的pattern的值也不应相同，这一点需要处理：在放入新的k-v pair时，需要判断是否已含有这个value。

public class Solution {
    public boolean wordPattern(String pattern, String str) {
        String[] attr = str.split(" ");
        if(pattern.length() != attr.length) return false;
        Map<Character, String> map = new HashMap<Character, String>();
        for(int i = 0; i < pattern.length(); i++) {
            char c = pattern.charAt(i);
            if(map.containsKey(c)) {
                if(!map.get(c).equals(attr[i])) {
                    return false;
                }
            } else {
                if(map.containsValue(attr[i])) {
                    return false;
                }
                map.put(c, attr[i]);
            }
        }
        return true;
    }
}