LeetCode: 290. 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​​.

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 that may be separated by a single space.

解题思路 —— 哈希

由于 ​​pattern​​​ 是小写字母组成，因此可以用 ​​pattern[i] - 'a'​​​ 来映射 ​​pattern[i]​​​。
因此就可以用 ​​​var wordsMap [26]string​​​ 数组来存放 ​​pattern​​​ 和 ​​str​​ 中的单词的映射关系。

AC 代码

func wordPattern(pattern string, str string) bool {
    words := strings.Split(str, " ")
    var wordsMap [26]string
    
    if len(pattern) != len(words) {
        return false
    }
    
    for i := 0; i < len(words); i++{
        if wordsMap[pattern[i]-'a'] == "" {
            for j := 0; j < len(wordsMap); j++{
                if wordsMap[j] == words[i] {
                    return false
                }
            }
            wordsMap[pattern[i]-'a'] = words[i]
        } else if wordsMap[pattern[i]-'a'] != words[i] {
            return false
        }
    }
    
    return true
}