LeetCode290 Word Pattern

题目描述

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:
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.

题目解析

解题思路

每一对匹配的模式看成一个（key， value）

代码实现

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

            }
        }
        return true;
    }
}