Valid Palindrome

leetcode:https://oj.leetcode.com/problems/

今天A了一个Easy类型的，主要是判断一个字符串是否是回文。东平西凑的还是给弄好了，具体可看下面的要求，或者直接去网站上看也行

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.

 public class Solution {
     public boolean isPalindrome(String str){
         char array[] = str.toCharArray();
         int i = 0;
         int j = array.length -  1;
         boolean isPal = true;
         if(str.length() == 0)
             return true;
         else if(str.length() == 1)
             return true;
         while(i <= j){
             while(!isNumOrAlp(array[i++]) && i < array.length);
             while(!isNumOrAlp(array[j--]) && j >= 0);
             i--;
             j++;
             if(!isEqual(array[i], array[j]))
             {
                 isPal = false;
                 break;
             }
             i++;
             j--;
         }
         if(isPal)
             return true;

         else
             return false;

     }
     public boolean isNumOrAlp(char ch){
         if(ch >= '0' && ch <= '9')
             return true;
         else if(ch >= 'a' && ch <= 'z')
             return true;
         else if(ch >= 'A' && ch <= 'Z')
             return true;
         else
             return false;
     }
     public boolean isEqual(char ch1,char ch2){
         if(0 == ch1 - ch2)
             return true;
         else if(32 == Math.abs(ch2 - ch1))
             return true;
         else if(!isNumOrAlp(ch1) && !isNumOrAlp(ch2)){
             return true;
         }
         else
             return false;
     }
 }

这个还是比较简单的，所以就没注释了。很多细节的地方需要注意，oj系统给出错误信息都能很好定位问题在哪儿