【Leetcode】29. Divide Two Integers

Description

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
Note:

Both dividend and divisor will be 32-bit signed integers.
The divisor will never be 0.
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 231 − 1 when the division result overflows.

Solution

# @param {Integer} dividend
# @param {Integer} divisor
# @return {Integer}
def divide(dividend, divisor)
    sign = (dividend.negative? == divisor.negative?) ? 1 : -1

    num1 = dividend.abs
    num2 = divisor.abs

    result = 0
    mid    = 31
    while num1 >= num2 do
        i, j = 0, mid
        while i <= j do
            mid = (i + j)/2
            break if num2 << mid <= num1 && num2 << (mid + 1) > num1
            num2 << mid > num1 ? j = mid - 1 : i = mid + 1
        end

        return sign > 0 ? (2**31 - 1) : ~(2**31 - 1)  if mid > 30

        num1 -= num2 << mid
        result += 2 ** mid
    end

    result * sign
end