1079. typography

First, write your own. . 17% of the time, space 100%, which is set to re-do the results?

set<string> res;
vector<string> temp;
vector<bool> ok;
void back(string s)
{
    for (int i = 0; i < temp.size(); i++)
    {
        if (ok[i])
        {
            ok[i] = false;
            s += temp[i];
            res.insert(s);
            back(s);
            ok[i] = true;
            s.pop_back();
        }
    }
}
int numTilePossibilities(string tiles) {
    for (int i = 0; i < tiles.size(); i++)
    {
        temp.push_back(tiles.substr(i, 1));
    }
    for (int i = 0; i < tiles.size(); i++)
        ok.push_back(true);
    string s="";
    back(s);
    return res.size();
}

Second, the problem solution

If nothing particularly good algorithm. . Well, look at what it is tomorrow dictionary tree. .