Submission #605829

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
605829	2022-07-26T03:06:43 Z	buidangnguyen05	Network (BOI15_net)	C++14	18 / 100	9 ms	12128 KB

net

//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();
			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);
	}
 
	int root = 0, save1 = 0, save2 = 0;
	for (int i = 1; i <= n; ++i) {
		if (adj[i].size() > 1) root = i;
		else if (!save1) save1 = i;
		else save2 = i;
	}
	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";
}

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	7 ms	11988 KB	Output is correct
2	Correct	6 ms	11988 KB	Output is correct
3	Correct	8 ms	12020 KB	Output is correct
4	Correct	7 ms	11988 KB	Output is correct
5	Correct	6 ms	11988 KB	Output is correct
6	Correct	7 ms	11988 KB	Output is correct
7	Correct	6 ms	11960 KB	Output is correct
8	Correct	6 ms	11988 KB	Output is correct
9	Correct	6 ms	11988 KB	Output is correct
10	Correct	6 ms	11988 KB	Output is correct
11	Correct	6 ms	11988 KB	Output is correct
12	Correct	6 ms	12060 KB	Output is correct
13	Correct	6 ms	11988 KB	Output is correct
14	Correct	8 ms	12116 KB	Output is correct
15	Correct	7 ms	12068 KB	Output is correct
16	Correct	7 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	6 ms	11988 KB	Output is correct
20	Correct	6 ms	11988 KB	Output is correct

Subtask #2

0 / 45.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	7 ms	11988 KB	Output is correct
2	Correct	6 ms	11988 KB	Output is correct
3	Correct	8 ms	12020 KB	Output is correct
4	Correct	7 ms	11988 KB	Output is correct
5	Correct	6 ms	11988 KB	Output is correct
6	Correct	7 ms	11988 KB	Output is correct
7	Correct	6 ms	11960 KB	Output is correct
8	Correct	6 ms	11988 KB	Output is correct
9	Correct	6 ms	11988 KB	Output is correct
10	Correct	6 ms	11988 KB	Output is correct
11	Correct	6 ms	11988 KB	Output is correct
12	Correct	6 ms	12060 KB	Output is correct
13	Correct	6 ms	11988 KB	Output is correct
14	Correct	8 ms	12116 KB	Output is correct
15	Correct	7 ms	12068 KB	Output is correct
16	Correct	7 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	6 ms	11988 KB	Output is correct
20	Correct	6 ms	11988 KB	Output is correct
21	Correct	6 ms	11988 KB	Output is correct
22	Correct	7 ms	12116 KB	Output is correct
23	Correct	7 ms	12116 KB	Output is correct
24	Correct	7 ms	12072 KB	Output is correct
25	Correct	7 ms	12080 KB	Output is correct
26	Correct	7 ms	12116 KB	Output is correct
27	Correct	9 ms	12128 KB	Output is correct
28	Correct	7 ms	12072 KB	Output is correct
29	Correct	7 ms	12064 KB	Output is correct
30	Correct	6 ms	12056 KB	Output is correct
31	Incorrect	7 ms	12076 KB	Breaking single line is causing network to disconnect.
32	Halted	0 ms	0 KB	-

Subtask #3

0 / 37.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	7 ms	11988 KB	Output is correct
2	Correct	6 ms	11988 KB	Output is correct
3	Correct	8 ms	12020 KB	Output is correct
4	Correct	7 ms	11988 KB	Output is correct
5	Correct	6 ms	11988 KB	Output is correct
6	Correct	7 ms	11988 KB	Output is correct
7	Correct	6 ms	11960 KB	Output is correct
8	Correct	6 ms	11988 KB	Output is correct
9	Correct	6 ms	11988 KB	Output is correct
10	Correct	6 ms	11988 KB	Output is correct
11	Correct	6 ms	11988 KB	Output is correct
12	Correct	6 ms	12060 KB	Output is correct
13	Correct	6 ms	11988 KB	Output is correct
14	Correct	8 ms	12116 KB	Output is correct
15	Correct	7 ms	12068 KB	Output is correct
16	Correct	7 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	6 ms	11988 KB	Output is correct
20	Correct	6 ms	11988 KB	Output is correct
21	Correct	6 ms	11988 KB	Output is correct
22	Correct	7 ms	12116 KB	Output is correct
23	Correct	7 ms	12116 KB	Output is correct
24	Correct	7 ms	12072 KB	Output is correct
25	Correct	7 ms	12080 KB	Output is correct
26	Correct	7 ms	12116 KB	Output is correct
27	Correct	9 ms	12128 KB	Output is correct
28	Correct	7 ms	12072 KB	Output is correct
29	Correct	7 ms	12064 KB	Output is correct
30	Correct	6 ms	12056 KB	Output is correct
31	Incorrect	7 ms	12076 KB	Breaking single line is causing network to disconnect.
32	Halted	0 ms	0 KB	-