LeetCode | Palindrome Number

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

click to show spoilers.

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.

判断一个整数是否是回文

显然负数不是，0 是。
要求不允许申请额外空间O(1)，那么只有通过取位数了

class Solution {public:    bool isPalindrome(int x) {        if(x<0) return false;        if(x==0) return true;        //获得这个数字的位数        int n=0,temp=x;        while(temp){            n++;temp/=10;        }        for(int i=0;i<n/2;i++){            //注意这里取位数的方法            if( (int)(x/pow(10,i))%10 != (int)(x/pow(10,n-1-i))%10 )            return false;        }        return true;    }};