[LeetCode]371. Sum of Two Integers

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.

class Solution {
public:
    int getSum(int a, int b) {
        //将十机制加法转化为二进制加法
        //非进位项用异或获得，进位项用与获得，进位项向左移位获得真正的进位数
        //重复这个操作直到不能再进位
        if(b == 0) return a;
        int nocarrynum = a ^ b;
        int carrynum = (a & b)<<1;
        return getSum(nocarrynum, carrynum);
    }
};