[leetcode]: 371. Sum of Two Integers

1.题目描述
Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -.
翻译：不使用+，-符号，计算两个整数的和
Example:
Given a = 1 and b = 2, return 3.

2.分析
首先想到电路里面加法器的实现：
保留位remain=a^b 0^1=1,1^0=1,0^0=0,1^1=0
进位carry=a&b<<1

3.代码

class Solution {
public:
    int getSum(int a, int b) {
        int remain = a;
        int carry = b;
        while (carry) {
            int temp = carry^remain;//异或
            carry = (carry&remain) << 1;//进位
            remain = temp;
        }
        return remain;
    }
};