9. Palindrome Number

题目

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

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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.

分析

从左到右计算一遍x，与从右到左的x比较，如果相等则是回文串，否则不是。

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