Leetcode#29 Divide Two Integers

class Solution {
public:
    int divide(int dividend, int divisor) {
        if (divisor == 0)
            return dividend >= 0 ? INT_MAX : INT_MIN;

        if (dividend == INT_MIN && divisor == -1)
            return INT_MAX;

        bool neg = false;

        if((dividend<0 && divisor>0) || (dividend>0 && divisor<0)) 
            neg = true;

        unsigned long long a_dividend = abs((long long)dividend);
        unsigned long long a_divisor = abs((long long)divisor);

        int i = 0;
        while(a_divisor << i < a_dividend)
            i++;

        int res = 0;
        while (a_divisor <= a_dividend) {
            if (a_dividend >= a_divisor << i) {
                res += 1<<i;
                a_dividend -= a_divisor << i;
            }
            i--;
        }

        return neg ? 0-res : res;   
    }
};