Specific ideas ：

The idea adopted here should pay attention to two points ：

1. In fact, it is equivalent to moving the carry left , Add again as an addend and a non carry number , Until the carry is 0 until ;

2. I want you to pay attention ,c++ Signed negative numbers are required and cannot be moved to the left at will , It's undefined behavior , Therefore, the number should be converted into an unsigned number and shifted to the left ;

It is worth noting that , The symbol is only used for decoration in the carry calculation , That is, positive and negative numbers can be calculated directly according to the same , Don't worry about the sign bit ;

Specific code ：

class Solution {
    
public:
    int add(int a, int b) {
    
        while(b!=0){
    
            int c=(a&b);
            a^=b;
            b=unsigned(c)<<1;
        }
        return a;
    }
};