每日算法之二十五：Divide Two Integers

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

不使用乘法、除法和求模运算求两个数相除。

class Solution {public:    long long internalDivide(unsigned long long dividend,unsigned long long divisor)    {      if(dividend<divisor)        return 0;      int result = 1;      unsigned long long temp = divisor,left;      while(temp<=dividend)      {        left = dividend - temp;        temp<<=1;        if(temp>dividend)          break;        else          result<<=1;      }      return result + internalDivide(left,divisor);    }    int divide(int dividend, int divisor) {      unsigned long long _dividend = abs(static_cast<long long>(dividend)),                         _division = abs(static_cast<long long>(divisor));        bool flag = ((dividend<=0)&&(divisor>0))|| ((dividend>=0)&&(divisor<0));      return flag?(-1)*internalDivide(_dividend,_division):internalDivide(_dividend,_division);    }};

简要分析，以87/4为例：4小于87,4左移一位变成8，计数左移一位变成2。8小于87，继续左移变成16，计数变成4.16小于87左移变成32，计数变成8。32小于87左移变成64，计数变成16。继续左移变成128大于87。87减去64 = 23。计数为16倍。用23继续上述步骤，知道