leetcode 371 不用加减求两数之和

//方法一，递归版
//Time::O(n),Space:O(1)
class Solution 
{
public:
    int Add(int num1, int num2)
    {
        return num2==0?num1:Add(num1^num2,(num1&num2)<<1);
    }
};

//方法二，迭代版
//Space::O(1),Time::O(n)

class Solution 
{
public:
    int Add(int num1, int num2)
    {
        while(num2!=0)
        {
            int sum=num1^num2;
            int carry=(num1&num2)<<1;
            
            num1=sum;
            num2=carry;
        }
        
        return num1;
    }
};