LeetCode 9. 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?

此題邏輯極爲簡單，Accepted代碼如下：

class Solution {
    public boolean isPalindrome(int x) {
        if (x < 0) {
            return false;
        } else if (x == 0) {
            return true;
        } else {
            int sum = 0;
            int a = x;
            while (a > 0) {
                sum = sum * 10 + a % 10;
                a /= 10;
            }
            return sum == x;
        }
        
    }
}

此解法RT小於61.6%，但空間居然僅小於7.64%的人，這實在令我費解，暫時還未發現有什麼特別省空間的操作。