29. Divide Two Integers

题目

Divide two integers without using multiplication, division and mod operator.

If it is overflow, return MAX_INT.

题意

比较经典的一道题，一直做减法运算，结果时间复杂度超了，网上查了一下，就用移位做的
对于那个-2147483648，给出2147483647，是因为超出最大值就将最大值返回了，不过我这个没考虑最大值问题，只是加了一个测试用例，accepted

Python实现

class Solution(object):
    def divide(self, dividend, divisor):
        """
        :type dividend: int
        :type divisor: int
        :rtype: int
        """
        if divisor == 0: return -1
        if dividend==-2147483648 and divisor==-1:return 2147483647
        num = 0
        if (divisor > 0 and dividend > 0) or (divisor<0 and dividend<0): flag = 0
        else:flag=1
        dividend=abs(dividend)
        divisor=abs(divisor)
        while dividend >= divisor:
            ni=1
            temp=divisor
            while temp<=dividend:
                temp=temp<<1
                if temp<=dividend:ni=ni<<1
            dividend=dividend-(temp>>1)
            num += ni
        if flag == 1: return -num
        return num