leetcode

0 class Solution {

1 int degree[21] = {0};

2 int res = 0;

3

4 void rec(const vector<vector<int>> &req, int cur = 0, int cnt = 0, int dirty = 0) {

5 if (cnt + (req.size() - cur) < res) return;

6 if (cur == req.size()) {

7 if (dirty) return;

8 res = max(res, cnt);

9 return;

10 }

11

12 rec(req, cur + 1, cnt, dirty);

13

14 if (degree[req[cur][0]]++ == 0) dirty++;

15 if (--degree[req[cur][1]] == 0) dirty--;

16 rec(req, cur + 1, cnt + 1, dirty);

17 degree[req[cur][0]]--, degree[req[cur][1]]++;

18 }

19

20 public:

21 int maximumRequests(int n, const vector<vector<int>> &requests) {

22 rec(requests);

23 return res;

24 }

25 };