Submission #605839

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
605839	2022-07-26T03:23:17 Z	buidangnguyen05	Network (BOI15_net)	C++14	63 / 100	498 ms	75576 KB

//source: https://oj.uz/problem/view/BOI15_net
 
#include<bits/stdc++.h>
using namespace std;
 
typedef long long ll;
 
const int N = 5e5 + 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();
			//cerr << x << " " << p << " " << q << "\n";
			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, save1 = 0, save2 = 0;
	for (int i = 1; i <= n; ++i) {
		if (adj[i].size() > 1 && !root) root = i;
		else if (adj[i].size() == 1 && !save1) save1 = i;
		else if (adj[i].size() == 1 && !save2) save2 = 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(), (save1 == rem.back() ? save2 : save1));
	cout << ans.size() << "\n";
	for (pair<int, int> i : ans) cout << i.first << " " << i.second << "\n";
	//system("graph_.exe");
}

Compilation message

net.cpp: In function 'int main()':
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.inp", "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
net.cpp:33:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   33 |   freopen("task.out", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
18.0 / 18.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	6 ms	11988 KB	Output is correct
2	Correct	6 ms	11988 KB	Output is correct
3	Correct	8 ms	11988 KB	Output is correct
4	Correct	6 ms	12060 KB	Output is correct
5	Correct	6 ms	11988 KB	Output is correct
6	Correct	6 ms	11992 KB	Output is correct
7	Correct	7 ms	11988 KB	Output is correct
8	Correct	6 ms	11988 KB	Output is correct
9	Correct	6 ms	12056 KB	Output is correct
10	Correct	6 ms	11988 KB	Output is correct
11	Correct	7 ms	12064 KB	Output is correct
12	Correct	7 ms	12060 KB	Output is correct
13	Correct	6 ms	11988 KB	Output is correct
14	Correct	7 ms	11988 KB	Output is correct
15	Correct	6 ms	11988 KB	Output is correct
16	Correct	6 ms	11988 KB	Output is correct
17	Correct	6 ms	11988 KB	Output is correct
18	Correct	6 ms	11988 KB	Output is correct
19	Correct	8 ms	11988 KB	Output is correct
20	Correct	7 ms	11988 KB	Output is correct

Subtask #2
45.0 / 45.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	6 ms	11988 KB	Output is correct
2	Correct	6 ms	11988 KB	Output is correct
3	Correct	8 ms	11988 KB	Output is correct
4	Correct	6 ms	12060 KB	Output is correct
5	Correct	6 ms	11988 KB	Output is correct
6	Correct	6 ms	11992 KB	Output is correct
7	Correct	7 ms	11988 KB	Output is correct
8	Correct	6 ms	11988 KB	Output is correct
9	Correct	6 ms	12056 KB	Output is correct
10	Correct	6 ms	11988 KB	Output is correct
11	Correct	7 ms	12064 KB	Output is correct
12	Correct	7 ms	12060 KB	Output is correct
13	Correct	6 ms	11988 KB	Output is correct
14	Correct	7 ms	11988 KB	Output is correct
15	Correct	6 ms	11988 KB	Output is correct
16	Correct	6 ms	11988 KB	Output is correct
17	Correct	6 ms	11988 KB	Output is correct
18	Correct	6 ms	11988 KB	Output is correct
19	Correct	8 ms	11988 KB	Output is correct
20	Correct	7 ms	11988 KB	Output is correct
21	Correct	5 ms	12008 KB	Output is correct
22	Correct	7 ms	12116 KB	Output is correct
23	Correct	7 ms	12116 KB	Output is correct
24	Correct	6 ms	12116 KB	Output is correct
25	Correct	7 ms	12056 KB	Output is correct
26	Correct	6 ms	12104 KB	Output is correct
27	Correct	7 ms	12116 KB	Output is correct
28	Correct	9 ms	12136 KB	Output is correct
29	Correct	8 ms	12116 KB	Output is correct
30	Correct	7 ms	11988 KB	Output is correct
31	Correct	6 ms	12116 KB	Output is correct
32	Correct	7 ms	11988 KB	Output is correct
33	Correct	7 ms	11988 KB	Output is correct
34	Correct	9 ms	11988 KB	Output is correct
35	Correct	7 ms	11988 KB	Output is correct
36	Correct	6 ms	11988 KB	Output is correct
37	Correct	6 ms	12116 KB	Output is correct
38	Correct	6 ms	12116 KB	Output is correct
39	Correct	6 ms	11988 KB	Output is correct
40	Correct	6 ms	11936 KB	Output is correct
41	Correct	8 ms	11988 KB	Output is correct
42	Correct	7 ms	11988 KB	Output is correct
43	Correct	8 ms	12060 KB	Output is correct
44	Correct	6 ms	11988 KB	Output is correct
45	Correct	6 ms	11956 KB	Output is correct
46	Correct	7 ms	12008 KB	Output is correct
47	Correct	6 ms	11988 KB	Output is correct
48	Correct	7 ms	11964 KB	Output is correct
49	Correct	7 ms	11988 KB	Output is correct
50	Correct	6 ms	11988 KB	Output is correct
51	Correct	7 ms	12064 KB	Output is correct
52	Correct	6 ms	11988 KB	Output is correct
53	Correct	8 ms	12072 KB	Output is correct
54	Correct	6 ms	11988 KB	Output is correct
55	Correct	7 ms	11988 KB	Output is correct
56	Correct	6 ms	11988 KB	Output is correct
57	Correct	6 ms	12028 KB	Output is correct
58	Correct	8 ms	12116 KB	Output is correct

Subtask #3
0 / 37.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	6 ms	11988 KB	Output is correct
2	Correct	6 ms	11988 KB	Output is correct
3	Correct	8 ms	11988 KB	Output is correct
4	Correct	6 ms	12060 KB	Output is correct
5	Correct	6 ms	11988 KB	Output is correct
6	Correct	6 ms	11992 KB	Output is correct
7	Correct	7 ms	11988 KB	Output is correct
8	Correct	6 ms	11988 KB	Output is correct
9	Correct	6 ms	12056 KB	Output is correct
10	Correct	6 ms	11988 KB	Output is correct
11	Correct	7 ms	12064 KB	Output is correct
12	Correct	7 ms	12060 KB	Output is correct
13	Correct	6 ms	11988 KB	Output is correct
14	Correct	7 ms	11988 KB	Output is correct
15	Correct	6 ms	11988 KB	Output is correct
16	Correct	6 ms	11988 KB	Output is correct
17	Correct	6 ms	11988 KB	Output is correct
18	Correct	6 ms	11988 KB	Output is correct
19	Correct	8 ms	11988 KB	Output is correct
20	Correct	7 ms	11988 KB	Output is correct
21	Correct	5 ms	12008 KB	Output is correct
22	Correct	7 ms	12116 KB	Output is correct
23	Correct	7 ms	12116 KB	Output is correct
24	Correct	6 ms	12116 KB	Output is correct
25	Correct	7 ms	12056 KB	Output is correct
26	Correct	6 ms	12104 KB	Output is correct
27	Correct	7 ms	12116 KB	Output is correct
28	Correct	9 ms	12136 KB	Output is correct
29	Correct	8 ms	12116 KB	Output is correct
30	Correct	7 ms	11988 KB	Output is correct
31	Correct	6 ms	12116 KB	Output is correct
32	Correct	7 ms	11988 KB	Output is correct
33	Correct	7 ms	11988 KB	Output is correct
34	Correct	9 ms	11988 KB	Output is correct
35	Correct	7 ms	11988 KB	Output is correct
36	Correct	6 ms	11988 KB	Output is correct
37	Correct	6 ms	12116 KB	Output is correct
38	Correct	6 ms	12116 KB	Output is correct
39	Correct	6 ms	11988 KB	Output is correct
40	Correct	6 ms	11936 KB	Output is correct
41	Correct	8 ms	11988 KB	Output is correct
42	Correct	7 ms	11988 KB	Output is correct
43	Correct	8 ms	12060 KB	Output is correct
44	Correct	6 ms	11988 KB	Output is correct
45	Correct	6 ms	11956 KB	Output is correct
46	Correct	7 ms	12008 KB	Output is correct
47	Correct	6 ms	11988 KB	Output is correct
48	Correct	7 ms	11964 KB	Output is correct
49	Correct	7 ms	11988 KB	Output is correct
50	Correct	6 ms	11988 KB	Output is correct
51	Correct	7 ms	12064 KB	Output is correct
52	Correct	6 ms	11988 KB	Output is correct
53	Correct	8 ms	12072 KB	Output is correct
54	Correct	6 ms	11988 KB	Output is correct
55	Correct	7 ms	11988 KB	Output is correct
56	Correct	6 ms	11988 KB	Output is correct
57	Correct	6 ms	12028 KB	Output is correct
58	Correct	8 ms	12116 KB	Output is correct
59	Correct	371 ms	30028 KB	Output is correct
60	Correct	434 ms	32096 KB	Output is correct
61	Correct	7 ms	11988 KB	Output is correct
62	Correct	7 ms	11988 KB	Output is correct
63	Correct	289 ms	28204 KB	Output is correct
64	Correct	10 ms	13012 KB	Output is correct
65	Correct	19 ms	15884 KB	Output is correct
66	Correct	131 ms	46852 KB	Output is correct
67	Correct	431 ms	73832 KB	Output is correct
68	Correct	498 ms	75576 KB	Output is correct
69	Correct	13 ms	12696 KB	Output is correct
70	Correct	68 ms	19108 KB	Output is correct
71	Correct	279 ms	35124 KB	Output is correct
72	Correct	289 ms	34364 KB	Output is correct
73	Correct	91 ms	17360 KB	Output is correct
74	Correct	429 ms	31060 KB	Output is correct
75	Correct	27 ms	14636 KB	Output is correct
76	Correct	309 ms	34784 KB	Output is correct
77	Correct	289 ms	35188 KB	Output is correct
78	Incorrect	27 ms	17492 KB	Breaking single line is causing network to disconnect.
79	Halted	0 ms	0 KB	-

Submission #605839

Compilation message

Subtask #1 18.0 / 18.0

Subtask #2 45.0 / 45.0

Subtask #3 0 / 37.0

Subtask #1
18.0 / 18.0

Subtask #2
45.0 / 45.0

Subtask #3
0 / 37.0