Palindrome Number

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

没明白这句话“Do this without extra space.”是什么意思，A完以后看了别人的讨论也都用到了局部变量。

class Solution {
public:
    bool isPalindrome(int x) {
    if (x < 0)
        return false;
    if (x == 0)
        return true;
    int reverse = 0;
    int back_x = x;

    while (x > 0)
    {
        reverse = reverse * 10 + x % 10;
        x = x / 10;
    }

    if (back_x == reverse)
        return true;
    else
        return false;
    }
};