Solution.java

import java.util.HashMap;
import java.util.Map;

/**
 * User: Changle
 * Date: 2018-03-11 12:42
 * Source: https://leetcode.com/problems/word-pattern/description/
 */

/**
 * 把字符与字符串对应放入 map 中。
 *
 * 时间复杂度: O(n)
 * 空间复杂度: O(n)
 */
public class Solution {

    public boolean wordPattern(String pattern, String str) {
        String[] words = str.split(" ");
        if (pattern.length() != words.length) {
            return false;
        }

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

        for (int i = 0; i < pattern.length(); i++) {
            char c = pattern.charAt(i);
            if (map.containsKey(c)) {
                if (!map.get(c).equals(words[i])) {
                    return false;
                }
            } else {
                if (map.containsValue(words[i])) {
                    return false;
                }
                map.put(c, words[i]);
            }
        }
        return true;
    }
}