二、整数反转

示例 1:

输入: 123
输出: 321
 示例 2:

输入: -123
输出: -321
示例 3:

输入: 120
输出: 21

class Solution {
    public int reverse(int x) {
        int res = 0;
          while(x !=0){
              int temp = res * 10 + x % 10;
              if(temp / 10 != res)
                  return 0;
              res = temp;
              x = x / 10;
         }
         return res;
    }
}