题目描述：

Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.

Example:
Given a = 1 and b = 2, return 3.

代码实现：

class Solution {
public:
    int getSum(int a, int b) {
        return b==0?a:getSum(a^b,(a&b)<<1);
    }
};