【一天一道LeetCode】#9. Palindrome Number

一天一道LeetCode系列

（一）题目

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.

（二）解题

题目需要判断一个整数是不是回文数。需要注意一下几点：、

1、负数不是回文数

2、回文数满足反转后与原数相等，在反转整数那一题里面提到需要考虑越界问题，所以需要将int转换成long来处理。

代码比较简单，如下：

class Solution {
public:
    bool isPalindrome(int x) {
        if(x<0) return false;
        else{
            long n = 0;
            long temp = x;//考虑到反过来越界
            long lx = x;
            while(temp)
            {
                n = n*10+temp%10;//反转int数
                temp = temp/10;
            }
            if(n==lx) return true; //与原数相等则返回true
            else return false;
        }
    }
};