29. 两数相除

这种题目多考虑变成long，扩大精度

class Solution {
    public int divide(int dividend, int divisor) {
        long result = divideLong(dividend, divisor);
        return result > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) result;
    }

    public long divideLong(long dividend, long divisor) {
        boolean flag = dividend <0 != divisor <0;
        if(dividend < 0) dividend = - dividend;
        if(divisor<0) divisor = -divisor;
        if(dividend < divisor) return 0l;
        long sum = divisor;
        int num = 1;
        while((sum + sum) < dividend) {
            num += num;
            sum += sum;
        }
        return flag?-num-divideLong(dividend-sum, divisor):
    num+divideLong(dividend-sum,divisor);
    }
}