[LeetCode] Divide Two Integers( bit + 二分法 )

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

常常出现大的负数，无法用abs()转换成正数的情况

class Solution{
private:
    vector<long long> f;
public:
    int bsearch(vector<long long> &a,int left,int right,long long key){
        if(left > right)
            return -1;

        int mid = left + (right-left)/2;
        if(a[mid]==key)
            return mid;
        else if(a[mid]<key){
           int pos = bsearch(a,mid+1,right,key);
           return pos == -1 ?mid :pos;
        }else
            return bsearch(a,left,mid-1,key);
    }

    int divide(int devidend,int divisor){
        int sign = devidend <0 ?-1:1;
        if(divisor<0)
            sign *= -1;

        long long div = devidend;
        div = abs(div);
        long long divisorL = divisor;
        divisorL = abs(divisorL);
        f.push_back(divisorL);
        int size = 1;

        while(true){
            if(f[size-1] >= div)
                break;
            f.push_back(f[size-1]+f[size-1]);
            size++;
        }//end while

        int num = 0;
        long long sum = 0;
        while(div>0){
           int pos = bsearch(f,0,size-1,div);
           if(pos == -1)
               break;
           div -= f[pos];
           num += (1<< pos);
        }//end while
       return num*sign;
    }
};