Palindrome Number_LeetCode

Description:

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.

 

解题思路：

此题为回文数字的判定。

我的做法是让一个新的变量来存储倒置过来的数字，最后将这个新得到的数字和原数字进行比较。

如果两个数字相同，则这个数字是回文数字；否则，就不是回文数字。

核心思想和上一道数字的倒置一样。

有一点不同的是，负数在倒置前应该直接判定为非回文数字，0-10的个位数可以在倒置前直接判定为回文数字。

 

 

代码：

class Solution {
public:
    bool isPalindrome(int x) {
        int reserved = 0;
        int present = 0;
        present = x;
        if (present < 0) {
            return false;
        }
        if (present < 10) {
            return true;
        }
        while(x) {
            reserved = reserved*10 + x%10;
            x = x/10;
        }
        
        if (present == reserved) {
            return true;
        } else {
            return false;
        }
    }
};