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