Palindrome Number

Determine whether an integer is a palindrome. Do this without extra space.

click to show spoilers.

Some hints:

Could negative integers be palindromes? (ie, -1)

If you are thinking of converting the integer to string, note the restriction of using extra space.

You could also try reversing an integer. However, if you have solved the problem "Reverse Integer", you know that the reversed integer might overflow. How would you handle such case?

There is a more generic way of solving this problem.

考察的就是对数字每一位的操作。知道了/和%如何工作的那么提出数字的每一位都不是什么难事。只要每次比较数字的第一位和最后一位，看是否相等，然后去掉首位两位进行下一次循环。这里没有溢出什么的事情，还算比较简单。

public class Solution {
    public boolean isPalindrome(int x) {
        if(x < 0)
            return false;
        
        int div = 1;
        int temp = x;
        while((temp /= 10) > 0)
            div *= 10;
        
        while(x > 0){
            //compare the first and the last digit
            if(x % 10 != x / div)
                return false;
            //remove the first digit
            x %= div;
            //remove the last digit
            x /= 10;
            
            div /= 100;
        }
        return true;
    }
}