LeetCode 125 Valid Palindrome 回文字符串

描述

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.

Given a string s, return true if it is a palindrome, or false otherwise.

Example 1:

Input: s = "A man, a plan, a canal: Panama"
Output: true
Explanation: "amanaplanacanalpanama" is a palindrome.
Example 2:

Input: s = "race a car"
Output: false
Explanation: "raceacar" is not a palindrome.
Example 3:

Input: s = " "
Output: true
Explanation: s is an empty string "" after removing non-alphanumeric characters.
Since an empty string reads the same forward and backward, it is a palindrome.

来源：力扣（LeetCode）
链接：https://leetcode.cn/problems/valid-palindrome
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题解

/**
 * 忽略大小写
 * 空字符串默认为true
 * 首先正则去掉非字母和数字的字符
 * 然后双指针从两端开始遍历，只要有一个不相等就返回false
 * @param {string} s
 * @return {boolean}
 */
var isPalindrome = function (s) {
    const newStr = s.replace(/[^A-Za-z0-9]/g, '')
    if (newStr === '') return true
    let left = 0, right = newStr.length - 1
    while(left < right){
        if(newStr[left].toLocaleLowerCase() !== newStr[right].toLocaleLowerCase()){
            return false 
        }
        left ++
        right -- 
    }
    return true 
};