#!/usr/bin/env python
# -*- coding: utf-8 -*-
# author:ShidongDu time:2020/3/7
'''
【题目】
给定两个32位整数a和b,可正、可负、可0。不能使用算术运算符,分别实现a和b的加减乘除运算。
【要求】
如果给定的a和b执行加减乘除的某些结果本来就会导致数据的溢出,那么你实现的函数不必对那些结果负责。
'''
# 方法一
class Solution:
def multi(self, a, b):
return b and ((b & 1 and a) + self.multi(a<<1, b>>1))
solution = Solution()
res = solution.multi(3, 2000)
print(res)
# 方法二
# 这里a,b均为整数
def add(a, b):
if b == 0:
return a
# a, b互为相反数
if a == -b:
return 0
flag = False
# 异号数之和大于0,转换加数符号
if a < 0 and b > 0:
if -a < b:
flag = True
a = -a
b = -b
if a > 0 and b < 0:
if a > -b:
flag = True
a = -a
b = -b
while b != 0:
res = a ^ b
b = (a & b) << 1
a = res
if flag is True:
res = -res
return res
def multi(a, b):
sign_a = 0 # a的符号位
sign_b = 0 # b的符号位
# 提取符号位
if a < 0:
sign_a = 1
a = -a
if b < 0:
sign_b = 1
b = -b
res = 0
while b != 0:
if b & 1 == 1:
res = add(res, a)
a = a << 1
b = b >> 1
if sign_a ^ sign_b == 1:
res = -res
return res
print(multi(-3, 2))
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