【LeetCode】125.Valid Palindrome

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题目：

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.

解答：

一个从前往后遍历，一个从后往前遍历，剔除非字母非数字的字符，若不相等，则为假。

代码：

public class Solution {    public boolean isPalindrome(String s) {if(s == null || s.length() == 0)return true;char[] ac = s.toLowerCase().toCharArray();int i=0,j=ac.length-1;while(i<j){if(!isAlphaNumberic(ac[i])){i++;continue;}if(!isAlphaNumberic(ac[j])){j--;continue;}if(ac[i] != ac[j])return false;i++;j--;}return true;}public boolean isAlphaNumberic(char c){return Character.isAlphabetic(c) || Character.isDigit(c);}}

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