[LeetCode][JavaScript]Valid Palindrome

Valid Palindrome

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.

https://leetcode.com/problems/valid-palindrome/

 

 

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双指针，一个指向头，一个指向尾。如果不是字母数字，就继续找，head++， tail--。

 

/**
 * @param {string} s
 * @return {boolean}
 */
var isPalindrome = function(s) {
    s = s.trim();
    if(s !== ""){
        for(var i = 0, j = s.length - 1; i <= j; i++, j--){
            while(!/[a-z0-9]/i.test(s[i]) && i < s.length && i < j){
                i++;
            }
            while(!/[a-z0-9]/i.test(s[j]) && j > 0 && i < j){
                j--;
            }
            if(s[i].toUpperCase() !== s[j].toUpperCase()){
                return false;
            }
        }
    }
    return true;
};