leetcode 29: Divide Two Integers

class Solution {
public:
    int divide(int dividend, int divisor) {
        if(divisor==0||dividend==INT_MIN&&divisor==-1)
            return INT_MAX;
        long long a=labs(dividend);
        long long b=labs(divisor);
        int sign=(dividend>>31)^(divisor>>31)?-1:1;
        int res=0;
        while(a>=b)
        {
            long long c=b;
            int i=1;//number that divisor is multiplied by
            while(a>=c)
            {
                a-=c;
                res+=i;
                c<<=1;
                i<<=1;
            }
        }
        return sign==1?res:-res;
    }
};