LeetCode 124 Divide Two Integers

Divide two integers without using multiplication, division and mod operator.

分析：

不能用乘，除，取模来计算除法，只能用加减了，但一个一个减肯定不行。

每次使除数翻倍就可以了。

public class Solution {
    public int divide(int dividend, int divisor) {
        if(dividend==0 || divisor==0) return 0;
        //是否为负
        boolean isNeg = (dividend>0&&divisor<0)||(dividend<0&&divisor>0);
        long a = Math.abs((long)dividend);
        long b = Math.abs((long)divisor);
        //除数大于被除数
        if(b>a) return 0;
        long sum=0;
        long pow=0;
        int result=0;
        while(a>=b){
            pow=1;
            sum=b;
            //sum每次翻倍
            while(sum+sum<=a){
                sum += sum;
                pow += pow;
            }
            a -= sum;
            result += pow;
        }
        return isNeg ? -result : result;
    }
}