Java [Leetcode 125]valid palindrome

Title Description:

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:
Are you consider that the string might is empty? This was a good question to ask during a interview.

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

Problem Solving Ideas:

Set two pointers, one at the head of the string, one at the end of the string, the other in the middle, and a non-letter or number to move in the middle, such as two letters or numbers, then compare the two.

The code is as follows:

public class Solution {public    Boolean ispalindrome (String s) {    int i = 0, j = s.length ()-1;    char head, tail;    if (J < 0)    return true;    while (I < j) {    head = S.charat (i);    Tail = S.charat (j);    if (! Character.isletterordigit (head)) {    i++;    }     if (! Character.isletterordigit (tail)) {    j--;    }    if (Character.isletterordigit (head) && character.isletterordigit (tail)) {    if (character.tolowercase ( Head)! = Character.tolowercase (tail)) {    return false;    }    i++;    j--;    }    }    return true;    }}

　　

Java [Leetcode 125]valid palindrome