【LeetCode】#29两数相除(Divide Two Integers)

【LeetCode】#29两数相除(Divide Two Integers)

题目描述

给定两个整数，被除数 dividend 和除数 divisor。将两数相除，要求不使用乘法、除法和 mod 运算符。
返回被除数 dividend 除以除数 divisor 得到的商。

示例

示例 1:

输入: dividend = 10, divisor = 3
输出: 3

示例 2:

输入: dividend = 7, divisor = -3
输出: -2

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

Example 1:

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Input: dividend = 10, divisor = 3
Output: 3

Example 2:

Input: dividend = 7, divisor = -3
Output: -2

解法

class Solution {
    public int divide(int dividend, int divisor) {
        if (dividend == Integer.MIN_VALUE && divisor == -1) {
            return Integer.MAX_VALUE;
        }
        long a = Math.abs((long)dividend);
        long b = Math.abs((long)divisor);
        int num = 0;
        long sum;
        while (b <= a) {
            sum = b;
            int count = 1;
            while (sum + sum <= a) {
                count += count;
                sum += sum;
            }
            a = a - sum;
            num = num + count;
        }
        if ((dividend < 0 && divisor > 0) || dividend > 0 && divisor < 0) {
            num = -num;
        }
        return num;
    }
}