leetcode29 两数相除 int 与移位

难受啊

考虑越界

考虑dividend为-2^31，用负数移位运算

class Solution {
public:
    int divide(int dividend, int divisor) {
        
        if(dividend == divisor) 
            return 1;
        if(divisor == INT_MIN) 
            return 0;
        if(dividend==INT_MIN&&divisor==-1)
            return INT_MAX;
        if(dividend==INT_MIN&&divisor==1)
            return INT_MIN;
        int flag=(dividend>0)^(divisor>0);
    if (dividend > 0)
        dividend = -dividend;
    if (divisor > 0)
        divisor = -divisor;
    int n = 0;
    int count = 0;
    int temp = abs(divisor);
    int i;
    while (dividend <= divisor)
    {
        if (n == 31)
            break;
        i = -(temp << n);
        
        if (dividend > i)  //看成正数就是不够减
        {
            n--;
            if (n < 0)
                break;
        }
        else
        {
            dividend = dividend - i;
            count = count + (1 << n);
            if (dividend <= i)   //设i=1,2,4,8，...2^30 相加为2^31-1，此时n=30，若dividend还剩1，不加判断会导致上面temp<<31，越界
            {
                n++;
            }
        }
    }
        return flag ? -count : count;
    }
};