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29. Divide Two Integers

中文文档

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, which means losing its fractional part. For example, truncate(8.345) = 8 and truncate(-2.7335) = -2.

Note: Assume we are dealing with an environment that could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. For this problem, assume that your function returns 231 − 1 when the division result overflows.

 

Example 1:

Input: dividend = 10, divisor = 3
Output: 3
Explanation: 10/3 = truncate(3.33333..) = 3.

Example 2:

Input: dividend = 7, divisor = -3
Output: -2
Explanation: 7/-3 = truncate(-2.33333..) = -2.

Example 3:

Input: dividend = 0, divisor = 1
Output: 0

Example 4:

Input: dividend = 1, divisor = 1
Output: 1

 

Constraints:

  • -231 <= dividend, divisor <= 231 - 1
  • divisor != 0

Solutions

Python3

class Solution:
    def divide(self, a: int, b: int) -> int:
        INT_MAX = (1 << 31) - 1
        INT_MIN = -(1 << 31)
        sign = -1 if a * b < 0 else 1
        a = abs(a)
        b = abs(b)
        tot = 0
        while a >= b:
            cnt = 0
            while a >= (b << (cnt + 1)):
                cnt += 1
            tot += 1 << cnt
            a -= b << cnt
        return sign * tot if INT_MIN <= sign * tot <= INT_MAX else INT_MAX

Java

class Solution {
    public int divide(int a, int b) {
        int sign = 1;
        if ((a < 0) != (b < 0)) {
            sign = -1;
        }
        long x = Math.abs((long) a);
        long y = Math.abs((long) b);
        long tot = 0;
        while (x >= y) {
            int cnt = 0;
            while (x >= (y << (cnt + 1))) {
                cnt++;
            }
            tot += 1L << cnt;
            x -= y << cnt;
        }
        long ans = sign * tot;
        if (ans >= Integer.MIN_VALUE && ans <= Integer.MAX_VALUE) {
            return (int) ans;
        }
        return Integer.MAX_VALUE;
    }
}

Go

func divide(a int, b int) int {
	sign := 1
	if a*b < 0 {
		sign = -1
	}

	a = abs(a)
	b = abs(b)

	tot := 0
	for a >= b {
		cnt := 0
		for a >= (b << (cnt + 1)) {
			cnt++
		}
		tot += 1 << cnt
		a -= b << cnt
	}

	ans := sign * tot
	if ans >= math.MinInt32 && ans <= math.MaxInt32 {
		return ans
	}
	return math.MaxInt32
}

func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

C++

class Solution {
public:
    int divide(int a, int b) {
        int sign = 1;
        if (a < 0 ^ b < 0) {
            sign = -1;
        }

        auto x = abs(static_cast<long long>(a));
        auto y = abs(static_cast<long long>(b));
        auto tot = 0ll;
        while (x >= y) {
            int cnt = 0;
            while (x >= (y << (cnt + 1))) {
                ++cnt;
            }
            tot += 1ll << cnt;
            x -= y << cnt;
        }

        auto ans = sign * tot;
        if (ans >= INT32_MIN && ans <= INT32_MAX) {
            return static_cast<int>(ans);
        }
        return INT32_MAX;
    }
};

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