Day 13 - LeetCode 125. Valid Palindrome

LeetCode 125. Valid Palindrome

題目

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.

翻譯

給一個字串，不考慮大小寫與非字母數字的情況下，判斷這個字串是不是迴文。
範例：
"A man, a plan, a canal: Panama" --> true
"race a car" --> false (raceacar != racaecar)

注意：
你有考慮過空字串的情況嗎，在這邊我們定義空字串是一個迴文。

迴文: 正反字都是一樣

想法

1. 全轉小寫
2. 去除非字母還有數字
3. 反轉字串看是否相同

正規化：
https://chentsu.wordpress.com/2014/03/03/javascript-%E6%AD%A3%E8%A6%8F%E8%A1%A8%E9%81%94%E5%BC%8F-regexp-%E5%AF%AB%E6%B3%95/

詳細參閱

https://skyyen999.gitbooks.io/-leetcode-with-javascript/content/questions/125md.html

---

Code

/**
 * @param {string} s
 * @return {boolean}
 */
var isPalindrome = function(s) {
    //全部轉小寫, 去除非字母與數字
    s = s.toLowerCase().replace(/[^a-z0-9]/ig, '');
    //reverse_str =  s 倒轉
    var reverse_str =  s.split('').reverse().join('');

    return s === reverse_str;
};

isPalindrome('AQWE EWQA');//true
isPalindrome('ZXC_CXZ');//true
isPalindrome('ASD2FG');//false

Run

Your input
""
" "
"AQWE EWQA"
"ZXC_CXZ"
"ASD2FG"

Your answer
true
true
true
true
false

Expected answer
true
true
true
true
false

Runtime: 99 ms