leetcode題解||Palindrome Number問題

problem：

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.

(1)之前求過int型逆序反轉，這裡檢驗一個數是否為一個回文數，可以得到一點啟發。

（2）逆序反轉主要涉及溢出問題的處理，而且反轉的空間復雜度可以忽略不計，滿足題目要求。

code:

class Solution {
public:
    bool isPalindrome(int x) {
        int b=0;
        int a=x;
        bool flag=true;
        if(a<0)
        {
            bool flag=false;
            a=-x;
        }
        while(a)
        {
            b*=10;
            b+=a%10;
            a=a/10;
        }
        if(b>2147483647)
            return false;
        if(!flag)
            b=-b;
        return (b==x);
           
        
    }
};