LeetCode 504.七进制数

class Solution
{
public:
    string convertToBase7(int num)
    {
        //当num为0时
        if (num == 0)
        {
            //直接返回"0"
            return "0";
        }
        string res;
        bool flag = 0; //标记整数是否为负数
        if (num < 0)
        {
            flag = 1;
            num = -num;
        }
        while (num > 0)
        {
            res += '0' + num % 7;
            num /= 7;
        }
        //给res补上负号
        if (flag==true)
        {
            res += '-';
        }
        //反转字符串res得到结果
        reverse(res.begin(), res.end());
        return res;
    }
};