Divide Two Integers

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

思路：不能使用乘法除法以及取模运算来计算两个数相除。主要做法就是，将因子不断乘2（向左移位即可实现），同时结果从1不断移位加倍，等到除数大于被除数一半的时候，就从被除数中减去，将因子个数累加到结果中，再依次反复循环。跳出循环，不断递减的被除数与除数相等，则结果在加1.

class Solution {

public:

    int divide(int dividend, int divisor) {

        assert(divisor!=0);

        int result=0,count=0;

        bool isNeg=false;

        if((dividend>0&&divisor<0)||(dividend<0&&divisor>0))

            isNeg=true;

        unsigned int tDividend=abs(dividend);

        unsigned int tDivisor=abs(divisor);

        unsigned int tmp=0;

        while(tDividend>tDivisor)

        {

            count=1;

            tmp=tDivisor;

            while(tDividend>(tmp<<=1))

            {

                count<<=1;

            }

            tDividend-=(tmp>>1);

            result+=count;

        }

        if(tDividend==tDivisor)

        {

            result++;

        }

        return isNeg?(-result):result;

    }

};