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;
    }
};