题解1
题解2

图1

图2

图3

class Solution {
public:
    int add(int num1, int num2){
        while (num2) {
            int sum = num1 ^ num2;
            int carry = (num1 & num2) << 1; // 这里要加上括号, << 优先级比 & 高
            num1 = sum, num2 = carry;
        }
        return num1;
    }
};