# Palindrome Number

### 描述​

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

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.

### 代码​

// Palindrome Number// 时间复杂度O(1)，空间复杂度O(1)public class Solution {    public boolean isPalindrome(int x) {        if (x < 0) return false;        int d = 1; // divisor        while (x / d >= 10) d *= 10;        while (x > 0) {            int q = x / d;  // quotient            int r = x % 10;   // remainder            if (q != r) return false;            x = x % d / 10;            d /= 100;        }        return true;    }}