Leetcode：290. Word Pattern（JAVA）

【问题描述】

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.

【思路】

本题类似于205：Isomorphic Strings，分别使用一个HashMap匹配pair，以及HashSet避免两个映射到同一个str。

【code】

public class Solution {    public boolean wordPattern(String pattern, String str) {String[] s = str.split(" ");if (pattern.length() != s.length) {return false;}HashMap<Character, String> map = new HashMap<Character, String>();Stack<String> stack = new Stack<String>();Set<String> unique = new HashSet<String>();for (int i = 0; i < pattern.length(); i++) {if (map.containsKey(pattern.charAt(i))) {if (!map.get(pattern.charAt(i)).equals(s[i])) {return false;}}else {if (unique.contains(s[i])) {return false;}map.put(pattern.charAt(i), s[i]);unique.add(s[i]);}}return true;            }}