LeetCode Palidrome Number

class Solution {
public:
    bool isPalindrome(int x) {
        if (x < ) return false;
        int pow = ;
        int t = x;
        int cnt = ;
        while(t /= ) {
            pow *= ;
            cnt++;
        }
        t = x;
        cnt = cnt / ;
        while (cnt--) {
            if ((t / pow % ) != t % ) return false;
            t = t / ;
            pow /= ;
        }
        return true;
    }
};

500ms+,怎么会那么长时间

第二轮：

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

还是出了点差错，负数不算回文

// 19:50
class Solution {
public:
    bool isPalindrome(int x) {
        if (x < ) return false;
        int n = x;
        int cnt = ;

        do {
            cnt++;
            x = x/;
        } while (x);

        int tens = ;
        for (int i=; i<cnt; i++) {
            tens = tens*;
        }

        for (int i=cnt/-; i>=; i--) {
            int a = n / tens;
            int b = n % ;
            n = n - a * tens;
            n = n / ;
            if (a != b) {
                return false;
            }
            tens = tens/;
        }
        return true;
    }
};