see-504. Base 7

求十进制数的7进制表示法：辗转相除法

class Solution {
public:
    string convertToBase7(int num) {
        if(num==0)
            return "0";
        string ans="";
        int temp=num;
        
        num=abs(num);
        
        while(num!=0)
        {
            int mod=num%7;
            ans=to_string(mod)+ans;
            num/=7;
        } 
       if(temp<0)
           ans="-"+ans;
        return ans;
        
    }
};