leetcode 9 给一个int类型的数字，判断是否是回文数

题目要求：

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

Could negative integers be palindromes? (ie, -1)  负数返回false

If you are thinking of converting the integer to string, note the restriction of using extra space.不允许额外申请空间

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? 当使用了反转一个int类型的数据时，考虑会不会溢出

代码：

因为不可以申请新的空间，也最好不要反转int数字，那么考虑将x每次除以10得到余数，和x/（len-1）得到首位数进行比较

bool isPalindrome(int x) {    if(x<0)//复数返回fasle        return false；    int len=1;    int i=x;        //求出来x数字的位数    while(i/10>0)    {        i=i/10;        len++;    }      int tem1,tem2;     while(x>0)    {        tem1=x%10;        tem2=x/pow(10,(double)len-1);//10的n次方，函数pow（double x，double y）        if(tem1!=tem2)            return false;        else        {               x=x-tem1*pow(10,(double)len-1);            x=x/10;            len=len-2;        }    }    return true;}