Valid Palindrome

 

Total Accepted: 22728 

Total Submissions: 99271

Question  Solution 

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.

public class Solution {    public boolean isPalindrome(String s) {        if (s == null) {            return false;        }        if (s.length() == 0 || s.length() == 1) {            return true;        }        StringBuffer sb = new StringBuffer();        for (int i = 0; i < s.length();i++){            Character ch = s.charAt(i);	            if(Character.isLetter(ch) || Character.isDigit(ch)){                sb.append(Character.toUpperCase(ch));            } else {                continue;            }        }        int start = 0 ;        int end = sb.length() - 1;        while ( start < end) {            if (sb.charAt(start) == sb.charAt(end)) {                start ++;                end --;            } else {                return false;             }        }        return true;     }}

这个题目的问题在于刚開始的时候没有考虑到可能是数字的情况。题目本身没有难度。