Palindrome - 9. Palindrome Number

1. Palindrome Number

Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.

Example 1:

Input: 121 Output: true

Example 2:

Input: -121 Output: false Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.

Example 3:

Input: 10 Output: false Explanation: Reads 01 from right to left. Therefore it is not a palindrome.

Follow up:

Coud you solve it without converting the integer to a string?

思路：

判断数字是不是回文的，最简单的办法是把数组逆序，如果相同就是回文的，也可以通过截取首尾数字来判断是否是回文的数字。

代码：

java：

class Solution {

    public boolean isPalindrome(int x) {
        if (x < 0) return false;
        int rev = 0;
        int ori = x;
        while (x != 0) {
            rev = rev*10 + x%10;
            x /= 10;
        }
        return rev == ori;
    }
}