[leetcode]290.Word Pattern

Posted 2021-01-13 shinjia

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.

Example 1:

Input: pattern = "abba", str = "dog cat cat dog"
Output: true
Example 2:

Input:pattern = "abba", str = "dog cat cat fish"
Output: false
Example 3:

Input: pattern = "aaaa", str = "dog cat cat dog"
Output: false
Example 4:

Input: pattern = "abba", str = "dog dog dog dog"
Output: false
Notes:
You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.

解法

思路

用一个hashmap将pattern和str进行依次<key,value>映射即可。

代码

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