Divide Two Integers

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

比有趣在于1 提速过程 2怎么判断符号正负

 

public class Solution {

    public int divide(int dividend, int divisor) {

        long res =0, a = Math.abs((long) dividend), b=Math.abs((long) divisor), sum=0, pow = 0;

        if(b>a) return 0;

        // 中间加速环节相当于减去一个大b^pow， 然后剩下的部分再减去小的b^pow, ref： http://blog.csdn.net/perfect8886/article/details/23040143

        while(a>=b){

            sum=b;

            pow=1;

            while(a>=sum+sum){

                sum += sum;

                pow += pow;

            }

            a -= sum;

            res += pow;

        }

        //return isNeg ? -res:  res;

        res = (((dividend ^ divisor) >> 31) & 1)==1? -res:res;

        if(res>Integer.MAX_VALUE||res< Integer.MIN_VALUE)

            return Integer.MAX_VALUE;

        return (int) res;

        

    }

}