水题 唯一注意的点就是数字溢出

class Solution{
    public:  int reverse(int x)  {    long long MAX = ((long long)1 << 31) - 1;    long long MIN = 0 - (1 << 31);    long long a = 0;    while (x)    {      a = a * 10 + x % 10;      x /= 10;    }    return a > MAX || a < MIN ? 0 : a;  }};