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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;    }};