leetcode29 Divide Two Integers

"""
Given two integers dividend and divisor, divide two integers without using multiplication, division and mod operator.
Return the quotient after dividing dividend by divisor.
The integer division should truncate toward zero.
Example 1:
Input: dividend = 10, divisor = 3
Output: 3
Example 2:
Input: dividend = 7, divisor = -3
Output: -2
"""
"""
正确答案，先减第一个，再减double
"""
class Solution:
    def divide(self, dividend: int, divisor: int) -> int:
        res = 0
        positive = (dividend < 0) is (divisor < 0)
        dividend = abs(dividend)
        divisor = abs(divisor)
        while dividend >= divisor:
            temp, i = divisor, 1
            while dividend >= temp: #多加了一层循环，是为了避免超时
                res += i
                dividend -= temp
                i = 2*i
                temp = 2*temp
        if not positive:
            res = - res
        return min(max(-2147483648, res), 2147483647) #!!!这个范围限制很巧妙

"""
我的答案，一个一个减会超时
"""
class Solution:
    def divide(self, dividend, divisor):
        neg = 0
        res = 0
        if dividend > 0 and divisor < 0 or divisor > 0 and dividend < 0:
            neg = 1
        dividend = abs(dividend)
        divisor = abs(divisor)
        while dividend >= divisor:
            dividend = dividend - divisor
            res += 1
        if neg:
            res = - res
        return min(max(-2147483648, res), 2147483647)