Max sum from unique digits

Here i am finding maximum sum which can be formed by these (user input) numbers but numbers which are used to sum should not have any digit in common.

• We are given n numbers.
• We look at all subsets of this numbers,where every digit appears not more than once.
• For this subsets we calculate the sums.
• We are then looking for the maximum of this sums.

eg. input cases numbers n=4

0  1   2  3 - > 6  ( no repeated digits here ) 0+1+2+3
3  30  8  1 - > 39 ( here 3  is repeated so choose max from 3 & 30 i.e. 30) 30+8+1
11 21 31 41 - > 41 ( here 1 is repeated to all so max number will print ) 41
11 5  45 88 - > 99 ( here 5 is repeated so choose max from 45 & 5 i.e 45 ) 11+88+45


int sum(int Ticket[], int n)
{
    int max;
    int abc;
    for (int i = 0; i <= n; i++) {
        for (int k = 0; k <= n; k++) {
            abc = Ticket[i];
            max = Ticket[i] + Ticket[i]
                int len = to_string(abc).length();

            for (int j = 0; j <= len; j++) {
                std::string nstr = std::to_string(abc);
                std::cout << "->" << nstr[j];
            }
        }
    }
return max;
}
int main()
{ 
       // n total number of array or numbers
        int max = sum(Ticket, n);
}

quetion is how check uniqe digits of each numbers and form maximum sum.