[LeetCode] 125. Valid Palindrome

轉自LeetCode

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

For example,
"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.

Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.

For the purpose of this problem, we define empty string as valid palindrome.

<Solution>

這題是在處理 palindrom，但和找 Longest Palindromic Substring 有幾點不一樣

1. 不用算長度
2. input 有非字母的字元，像是空白、逗號等

解法不難，概念如下

• 兩個 pointer，一個從前面開始，一個從後面開始

• 遇到不是字母數字，就不要處理

• 字母都轉成小寫再比對

• 一旦有不一樣的，就回傳 false

code 如下

C++

Java

kotlin