[LeetCode]Palindrome Number

题目描述:(链接)

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

解题思路：

分离出首位，末位，分别比较！

class Solution {
public:
    bool isPalindrome(int x) {
        // 负数返回false
        if (x < 0) {
            return false;
        }
        
        int first = 0;
        int last = 0;
        
        // 计算x有多少位
        int len = 1;
        while (x / len >= 10) len *= 10;
        
        int div = 1;
        while (true) {
            if (len == 1) break;
            first = (x / len) % 10;
            last = (x / div) % 10;;
            if (first != last) {
                return false;
            }
            
            len /= 10;
            div *= 10;
        }
        
        return true;
    }
};