剑指offer--面试题47：不用加减乘除做加法

题目描述

写一个函数，求两个整数之和，要求在函数体内不得使用+、-、*、/四则运算符号。

python实现：

# -*- coding:utf-8 -*-
class Solution:
    def Add(self, num1, num2):
        # write code here
        if num1 == -num2:
            return 0
        result = 0
        num1 = num1&0xffffffff
        num2 = num2&0xffffffff
        MAXINT = 2**31-1
        while num2:
            c = num1^num2#c不同位
            num2 = (num1&num2)<<1#相同位
            num1 = c
            num1 = num1&0xffffffff
            num2 = num2&0xffffffff
        return num1 if num1<=MAXINT else -((~num1+1)&0x7fffffff)

c++实现：

class Solution {
public:
    //^表示加的值，&表示进位的值
    int Add(int num1, int num2)
    {
        if(num1==-num2)
            return 0;
        while(num2){
            int c = num1^num2;
            num2 = (num1&num2)<<1;
            num1 = c;
        }
        return num1;
    }
};