給定兩個整數，被除數 dividend 和除數 divisor。將兩數相除，要求不使用乘法、除法和 mod 運算子。

class Solution:
    def divide(self, a: int, b: int) -> int:
        # def mul(a, k):
        #     if a == 0 or k == 0:
        #         return 0
        #     if k == 1:
        #         return a
        #     if a == 1:
        #         return b
        #     return a + mul(a, k - 1)
        # 類比快速冪
        def mul(a, k):
            ans = 0
            while k:
                if k & 1:
                    ans += a
                k >>= 1
                a <<= 1
            return ans

        flag = -1 if a * b < 0 else 1
        a, b = abs(a), abs(b)

        l, r = 0, a
        ans = 0
        while l <= r:
            m = l + r >> 1
            if mul(m, b) <= a:
                l = m + 1
                ans = m
            else:
                r = m - 1

        ans *= flag
        maxInt = pow(2, 31) - 1
        if ans > maxInt or ans < -maxInt - 1:
            return maxInt
        return ans