Submission #605844

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
605844	2022-07-26T03:31:51 Z	buidangnguyen05	Network (BOI15_net)	C++14	100 / 100	463 ms	87212 KB

//source: https://oj.uz/problem/view/BOI15_net
 
#include<bits/stdc++.h>
using namespace std;
 
typedef long long ll;
 
const int N = 1e6 + 10;
vector<int> adj[N]; 
vector<pair<int, int>> ans;
 
vector<int> dfs(int x, int par) {
	if (adj[x].size() == 1) return vector<int>(1, x);
	vector<int> cur; 
	for (int i : adj[x]) if (i != par) {
		vector<int> v = dfs(i, x);
		if (cur.size() < v.size()) swap(v, cur);
		while (cur.size() + v.size() > 2 && v.size()) {
			int p = cur.back(); cur.pop_back();
			int q = v.back(); v.pop_back();
			ans.emplace_back(p, q);
		}
		for (int j : v) cur.push_back(j);
	}
	return cur;
}
 
signed main() {
	cin.tie(0)->sync_with_stdio(0);
	if (fopen("task.inp", "r")) {
		freopen("task.inp", "r", stdin);
		freopen("task.out", "w", stdout);
	}
	
	int n; cin >> n;
	for (int i = 1; i < n; ++i) {
		int x, y; cin >> x >> y;
		adj[x].push_back(y); adj[y].push_back(x);
		//ans.emplace_back(x, y);
	}
 
	int root = 0;
	for (int i = 1; i <= n; ++i) if (adj[i].size() > 1 && !root) root = i;
	//cerr << root << "\n";
	vector<int> rem = dfs(root, 0);
	if (rem.size() > 1) {
		int u = rem.back(); rem.pop_back();
		int v = rem.back(); rem.pop_back();
		ans.emplace_back(u, v);
	}
	if (rem.size()) ans.emplace_back(rem.back(), root);
	cout << ans.size() << "\n";
	for (pair<int, int> i : ans) cout << i.first << " " << i.second << "\n";
}

Compilation message

net.cpp: In function 'int main()':
net.cpp:31:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   31 |   freopen("task.inp", "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
net.cpp:32:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   32 |   freopen("task.out", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
18.0 / 18.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	10 ms	23764 KB	Output is correct
2	Correct	12 ms	23772 KB	Output is correct
3	Correct	11 ms	23692 KB	Output is correct
4	Correct	11 ms	23692 KB	Output is correct
5	Correct	11 ms	23764 KB	Output is correct
6	Correct	13 ms	23748 KB	Output is correct
7	Correct	11 ms	23736 KB	Output is correct
8	Correct	12 ms	23764 KB	Output is correct
9	Correct	13 ms	23764 KB	Output is correct
10	Correct	12 ms	23764 KB	Output is correct
11	Correct	14 ms	23792 KB	Output is correct
12	Correct	13 ms	23764 KB	Output is correct
13	Correct	12 ms	23728 KB	Output is correct
14	Correct	11 ms	23804 KB	Output is correct
15	Correct	11 ms	23764 KB	Output is correct
16	Correct	12 ms	23760 KB	Output is correct
17	Correct	11 ms	23764 KB	Output is correct
18	Correct	11 ms	23800 KB	Output is correct
19	Correct	11 ms	23764 KB	Output is correct
20	Correct	12 ms	23892 KB	Output is correct

Subtask #2
45.0 / 45.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	10 ms	23764 KB	Output is correct
2	Correct	12 ms	23772 KB	Output is correct
3	Correct	11 ms	23692 KB	Output is correct
4	Correct	11 ms	23692 KB	Output is correct
5	Correct	11 ms	23764 KB	Output is correct
6	Correct	13 ms	23748 KB	Output is correct
7	Correct	11 ms	23736 KB	Output is correct
8	Correct	12 ms	23764 KB	Output is correct
9	Correct	13 ms	23764 KB	Output is correct
10	Correct	12 ms	23764 KB	Output is correct
11	Correct	14 ms	23792 KB	Output is correct
12	Correct	13 ms	23764 KB	Output is correct
13	Correct	12 ms	23728 KB	Output is correct
14	Correct	11 ms	23804 KB	Output is correct
15	Correct	11 ms	23764 KB	Output is correct
16	Correct	12 ms	23760 KB	Output is correct
17	Correct	11 ms	23764 KB	Output is correct
18	Correct	11 ms	23800 KB	Output is correct
19	Correct	11 ms	23764 KB	Output is correct
20	Correct	12 ms	23892 KB	Output is correct
21	Correct	12 ms	23764 KB	Output is correct
22	Correct	12 ms	23908 KB	Output is correct
23	Correct	13 ms	23892 KB	Output is correct
24	Correct	11 ms	23892 KB	Output is correct
25	Correct	12 ms	23892 KB	Output is correct
26	Correct	12 ms	23764 KB	Output is correct
27	Correct	12 ms	23892 KB	Output is correct
28	Correct	12 ms	23888 KB	Output is correct
29	Correct	11 ms	23764 KB	Output is correct
30	Correct	11 ms	23764 KB	Output is correct
31	Correct	12 ms	23892 KB	Output is correct
32	Correct	14 ms	23764 KB	Output is correct
33	Correct	11 ms	23680 KB	Output is correct
34	Correct	14 ms	23764 KB	Output is correct
35	Correct	12 ms	23800 KB	Output is correct
36	Correct	11 ms	23752 KB	Output is correct
37	Correct	11 ms	23784 KB	Output is correct
38	Correct	11 ms	23848 KB	Output is correct
39	Correct	11 ms	23716 KB	Output is correct
40	Correct	11 ms	23804 KB	Output is correct
41	Correct	11 ms	23764 KB	Output is correct
42	Correct	11 ms	23744 KB	Output is correct
43	Correct	11 ms	23832 KB	Output is correct
44	Correct	13 ms	23764 KB	Output is correct
45	Correct	12 ms	23764 KB	Output is correct
46	Correct	13 ms	23844 KB	Output is correct
47	Correct	12 ms	23760 KB	Output is correct
48	Correct	11 ms	23784 KB	Output is correct
49	Correct	13 ms	23860 KB	Output is correct
50	Correct	11 ms	23764 KB	Output is correct
51	Correct	11 ms	23764 KB	Output is correct
52	Correct	13 ms	23764 KB	Output is correct
53	Correct	11 ms	23764 KB	Output is correct
54	Correct	13 ms	23764 KB	Output is correct
55	Correct	13 ms	23828 KB	Output is correct
56	Correct	11 ms	23764 KB	Output is correct
57	Correct	12 ms	23764 KB	Output is correct
58	Correct	11 ms	23892 KB	Output is correct

Subtask #3
37.0 / 37.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	10 ms	23764 KB	Output is correct
2	Correct	12 ms	23772 KB	Output is correct
3	Correct	11 ms	23692 KB	Output is correct
4	Correct	11 ms	23692 KB	Output is correct
5	Correct	11 ms	23764 KB	Output is correct
6	Correct	13 ms	23748 KB	Output is correct
7	Correct	11 ms	23736 KB	Output is correct
8	Correct	12 ms	23764 KB	Output is correct
9	Correct	13 ms	23764 KB	Output is correct
10	Correct	12 ms	23764 KB	Output is correct
11	Correct	14 ms	23792 KB	Output is correct
12	Correct	13 ms	23764 KB	Output is correct
13	Correct	12 ms	23728 KB	Output is correct
14	Correct	11 ms	23804 KB	Output is correct
15	Correct	11 ms	23764 KB	Output is correct
16	Correct	12 ms	23760 KB	Output is correct
17	Correct	11 ms	23764 KB	Output is correct
18	Correct	11 ms	23800 KB	Output is correct
19	Correct	11 ms	23764 KB	Output is correct
20	Correct	12 ms	23892 KB	Output is correct
21	Correct	12 ms	23764 KB	Output is correct
22	Correct	12 ms	23908 KB	Output is correct
23	Correct	13 ms	23892 KB	Output is correct
24	Correct	11 ms	23892 KB	Output is correct
25	Correct	12 ms	23892 KB	Output is correct
26	Correct	12 ms	23764 KB	Output is correct
27	Correct	12 ms	23892 KB	Output is correct
28	Correct	12 ms	23888 KB	Output is correct
29	Correct	11 ms	23764 KB	Output is correct
30	Correct	11 ms	23764 KB	Output is correct
31	Correct	12 ms	23892 KB	Output is correct
32	Correct	14 ms	23764 KB	Output is correct
33	Correct	11 ms	23680 KB	Output is correct
34	Correct	14 ms	23764 KB	Output is correct
35	Correct	12 ms	23800 KB	Output is correct
36	Correct	11 ms	23752 KB	Output is correct
37	Correct	11 ms	23784 KB	Output is correct
38	Correct	11 ms	23848 KB	Output is correct
39	Correct	11 ms	23716 KB	Output is correct
40	Correct	11 ms	23804 KB	Output is correct
41	Correct	11 ms	23764 KB	Output is correct
42	Correct	11 ms	23744 KB	Output is correct
43	Correct	11 ms	23832 KB	Output is correct
44	Correct	13 ms	23764 KB	Output is correct
45	Correct	12 ms	23764 KB	Output is correct
46	Correct	13 ms	23844 KB	Output is correct
47	Correct	12 ms	23760 KB	Output is correct
48	Correct	11 ms	23784 KB	Output is correct
49	Correct	13 ms	23860 KB	Output is correct
50	Correct	11 ms	23764 KB	Output is correct
51	Correct	11 ms	23764 KB	Output is correct
52	Correct	13 ms	23764 KB	Output is correct
53	Correct	11 ms	23764 KB	Output is correct
54	Correct	13 ms	23764 KB	Output is correct
55	Correct	13 ms	23828 KB	Output is correct
56	Correct	11 ms	23764 KB	Output is correct
57	Correct	12 ms	23764 KB	Output is correct
58	Correct	11 ms	23892 KB	Output is correct
59	Correct	352 ms	41764 KB	Output is correct
60	Correct	398 ms	43836 KB	Output is correct
61	Correct	11 ms	23764 KB	Output is correct
62	Correct	10 ms	23756 KB	Output is correct
63	Correct	284 ms	40040 KB	Output is correct
64	Correct	12 ms	24788 KB	Output is correct
65	Correct	20 ms	27700 KB	Output is correct
66	Correct	120 ms	58644 KB	Output is correct
67	Correct	424 ms	85608 KB	Output is correct
68	Correct	424 ms	87212 KB	Output is correct
69	Correct	16 ms	24532 KB	Output is correct
70	Correct	77 ms	30852 KB	Output is correct
71	Correct	251 ms	46888 KB	Output is correct
72	Correct	327 ms	46160 KB	Output is correct
73	Correct	70 ms	29068 KB	Output is correct
74	Correct	409 ms	42780 KB	Output is correct
75	Correct	30 ms	26312 KB	Output is correct
76	Correct	282 ms	46576 KB	Output is correct
77	Correct	314 ms	46828 KB	Output is correct
78	Correct	34 ms	29268 KB	Output is correct
79	Correct	463 ms	85724 KB	Output is correct
80	Correct	12 ms	23948 KB	Output is correct
81	Correct	107 ms	33048 KB	Output is correct
82	Correct	349 ms	51300 KB	Output is correct
83	Correct	403 ms	49392 KB	Output is correct
84	Correct	385 ms	49384 KB	Output is correct
85	Correct	444 ms	49320 KB	Output is correct
86	Correct	385 ms	50424 KB	Output is correct
87	Correct	414 ms	50424 KB	Output is correct

Submission #605844

Compilation message

Subtask #1 18.0 / 18.0

Subtask #2 45.0 / 45.0

Subtask #3 37.0 / 37.0

Subtask #1
18.0 / 18.0

Subtask #2
45.0 / 45.0

Subtask #3
37.0 / 37.0