leetcode

0 class Solution {

1 unordered_set<string> us;

2 bool used[8] = {false};

3 string crnt;

4

5 void rec(const string &tiles) {

6 us.insert(crnt);

7 if (crnt.size() == tiles.size()) return;

8

9 for (int i = 0; i < tiles.size(); i++) {

10 if (used[i]) continue;

11 used[i] = true;

12 crnt.push_back(tiles[i]);

13 rec(tiles);

14 crnt.pop_back();

15 used[i] = false;

16 }

17 }

18

19 public:

20 int numTilePossibilities(const string tiles) {

21 rec(tiles);

22 return us.size() - 1;

23 }

24 };