技術標籤：java

class Solution {
    public int divide(int dividend, int divisor) {
        if(divisor == 1) return dividend;
        if(divisor == -1 && dividend == Integer.MIN_VALUE){//Integer.MIN_VALUE
            return Integer.MAX_VALUE;
        }
        if(divisor < 0 && dividend <
 
 0){
            return divide(-(long)dividend, -(long)divisor);
        }
        else if(dividend < 0 || divisor < 0){
            return -divide(Math.abs((long)dividend), Math.abs((long)divisor));//負號必須放前面
        }
        else return divide((long)dividend, (long)divisor);
    }

    public int
 
 divide(long dividend, long divisor){
        if (dividend < divisor) {
            return 0;
        }
        int count = 1;
        long sum = divisor;
        while(dividend >= sum){
            sum <<= 1;
            count <<= 1;
        }
        sum >>>= 1;//對正數而言，無符號和有符號右移沒有區別
 

        count >>>= 1;//為什麼是無符號右移
        return count + divide(dividend - sum, divisor);
    }
}

無符號右移：注意負數為整數的補碼：先反碼再+1