7 - Palindrome Number

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.

solution：此题与之前类似，需要考虑负数和越界问题，负数直接返回0，为了防止反转的数值越界，因此每次只取最高位和最低位进行比较，然后数值依此剥去这两位（大小变为原来的1/100）。

class Solution {
public:
    bool isPalindrome(int x) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
        if(x < 0)
            return false;
        
        int count = 1;
        while(x/count >= 10)
        {
            count *= 10;
        }
        
        while(x != 0)
        {
            int high = x/count;
            int low = x % 10;
            if(high != low)
                return false;
            
            x = (x % count) / 10;
            count = count /100;
        }
        
        return true;
    }
};