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。

返回被除數 dividend 除以除數 divisor 得到的商。

整數除法的結果應當截去（truncate）其小數部分，例如：truncate(8.345) = 8 以及 truncate(-2.7335) = -2

輸入: dividend = 10, divisor = 3

輸出: 3

解釋: 10/3 = truncate(3.33333..) = truncate(3) = 3

解法一

class Solution {
    public int divide(int dividend, int
 
 divisor) {
        if (dividend == Integer.MIN_VALUE && divisor == -1) return Integer.MAX_VALUE;
        if (dividend == Integer.MAX_VALUE && divisor == 1) return Integer.MAX_VALUE;
        int result = 0;
        boolean isNeg = (dividend < 0 ^ divisor < 0); 
        dividend = -Math.abs(dividend);
        divisor 
 
= -Math.abs(divisor);
        while (dividend <= divisor) {
            int d = divisor; 
            int cnt = 1; 
            while (dividend <= d && d >= -1073741824) {
                d = d << 1;
                cnt = cnt << 1;
            }
            if (dividend <= d) {
                dividend 
 
-= d;
                result += cnt;
            } else {
                dividend -= d >> 1;
                result += cnt >> 1;
            }
        }
        return isNeg ? -result : result;
    }
}

解法二

class Solution {
    public int divide(int dividend, int divisor) {
        if (dividend == Integer.MIN_VALUE && divisor == -1) return Integer.MAX_VALUE;
        if (dividend == Integer.MAX_VALUE && divisor == 1) return Integer.MAX_VALUE;
        int res = 0;
        boolean isNeg = (dividend < 0 ^ divisor < 0); 
        dividend = -Math.abs(dividend);
        divisor = -Math.abs(divisor);
        if(divisor < -1){
            while(dividend <= divisor){
                int tmp = 1;
                int div = divisor;
                while(div >= dividend - div){
                    div = div<<1;
                    tmp = tmp<<1; 
                }
                res += tmp;
                dividend -= div;
                
            }
        }else{
            res = 0 - dividend;
        }
        return isNeg ? -res : res;
    }
}

知識點：無

總結：無