Submission #394634

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
394634	2021-04-27T06:28:05 Z	hivakarami	Network (BOI15_net)	C++14	100 / 100	1376 ms	91800 KB

#include<bits/stdc++.h>
 
using namespace std;
 
typedef long long int ll;
typedef long double ld;
#define f first
#define s second
#define pb push_back
 
const int N = 5e5 + 100;
const ld inf = 1e8;
const ll mod = 1e9 + 7;

int r, par[N], sz[N], d[N];
vector<int> adj[N], l[N];
vector<pair<int, int>> ans;
set<pair<int, int>> st;

void dfs(int u)
{
	sz[u] = 0;
	for(auto x : adj[u])
	{
		if(x == par[u])
			continue;
		par[x] = u;
		dfs(x);
		sz[u] += sz[x];
	}
	
	if(int(adj[u].size()) == 1)
		sz[u] = 1;
}


int find(int u)
{
	//cout << u + 1 << endl;
	for(auto x : adj[u])
	{
		if(x != par[u] && sz[x] > sz[r]/2)
			return find(x);
	}
	return u;

}


void DFS(int u)
{
	for(auto x : adj[u])
	{
		if(x != par[u])
		{
			par[x] = u;
			DFS(x);
		}
	}
	
	if(adj[u].size() == 1)
		l[r].pb(u);
}



int main()
{
    
    ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);	
	
	int n;
	cin >> n;
	for(int i = 0; i < n - 1; i++)
	{
		int x, y;
		cin >> x >> y;
		x--; y--;
		adj[x].pb(y);
		adj[y].pb(x);
	}
	
	for(int i = 0; i < n; i++)
	{
		if(int(adj[i].size()) > 1)
		{
			r = i;
			break;
		}
	}
	par[r] = r;
	dfs(r);
	
	//cout << "///////////////////////" << endl;
	
	//for(int i = 0; i < n; i++)
		//cout << i + 1 << ' ' << sz[i] << ' ' << par[i] + 1 << ' ' << adj[i].size() << endl;
	
	
	int u = find(r);
	
	//cout << u << endl;
	
	par[u] = u;
	for(auto x : adj[u])
	{
		par[x] = u;
		r = x;
		DFS(x);
		d[x] = l[x].size();
		st.insert({-d[x], x});
	}
	
	
	while(st.size() >= 2)
	{
		int x = st.begin()->s;
		st.erase(st.begin());
		int y = st.begin()->s;
		st.erase(st.begin());
		
		d[x]--; d[y]--;
		ans.pb({l[x][d[x]], l[y][d[y]]});
		
		if(d[x])
			st.insert({-d[x], x});
		
		if(d[y])
			st.insert({-d[y], y});
	}
		
	if(st.size())
	{
		int x = st.begin() -> s;
		d[x]--;
		ans.pb({u, l[x][d[x]]});		
	}	

	cout << ans.size() << endl;
	for(auto it : ans)
		cout << it.f + 1 << ' ' << it.s + 1 << endl; 

	return 0;
}

Subtask #1
18.0 / 18.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	17 ms	23768 KB	Output is correct
2	Correct	18 ms	23756 KB	Output is correct
3	Correct	15 ms	23756 KB	Output is correct
4	Correct	15 ms	23756 KB	Output is correct
5	Correct	15 ms	23756 KB	Output is correct
6	Correct	15 ms	23716 KB	Output is correct
7	Correct	15 ms	23756 KB	Output is correct
8	Correct	15 ms	23756 KB	Output is correct
9	Correct	15 ms	23792 KB	Output is correct
10	Correct	15 ms	23824 KB	Output is correct
11	Correct	15 ms	23820 KB	Output is correct
12	Correct	17 ms	23756 KB	Output is correct
13	Correct	17 ms	23756 KB	Output is correct
14	Correct	15 ms	23756 KB	Output is correct
15	Correct	15 ms	23756 KB	Output is correct
16	Correct	15 ms	23748 KB	Output is correct
17	Correct	15 ms	23756 KB	Output is correct
18	Correct	15 ms	23724 KB	Output is correct
19	Correct	15 ms	23756 KB	Output is correct
20	Correct	15 ms	23884 KB	Output is correct

Subtask #2
45.0 / 45.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	17 ms	23768 KB	Output is correct
2	Correct	18 ms	23756 KB	Output is correct
3	Correct	15 ms	23756 KB	Output is correct
4	Correct	15 ms	23756 KB	Output is correct
5	Correct	15 ms	23756 KB	Output is correct
6	Correct	15 ms	23716 KB	Output is correct
7	Correct	15 ms	23756 KB	Output is correct
8	Correct	15 ms	23756 KB	Output is correct
9	Correct	15 ms	23792 KB	Output is correct
10	Correct	15 ms	23824 KB	Output is correct
11	Correct	15 ms	23820 KB	Output is correct
12	Correct	17 ms	23756 KB	Output is correct
13	Correct	17 ms	23756 KB	Output is correct
14	Correct	15 ms	23756 KB	Output is correct
15	Correct	15 ms	23756 KB	Output is correct
16	Correct	15 ms	23748 KB	Output is correct
17	Correct	15 ms	23756 KB	Output is correct
18	Correct	15 ms	23724 KB	Output is correct
19	Correct	15 ms	23756 KB	Output is correct
20	Correct	15 ms	23884 KB	Output is correct
21	Correct	14 ms	23760 KB	Output is correct
22	Correct	19 ms	23984 KB	Output is correct
23	Correct	19 ms	23972 KB	Output is correct
24	Correct	18 ms	23968 KB	Output is correct
25	Correct	18 ms	23980 KB	Output is correct
26	Correct	17 ms	23848 KB	Output is correct
27	Correct	17 ms	23884 KB	Output is correct
28	Correct	17 ms	23884 KB	Output is correct
29	Correct	17 ms	23848 KB	Output is correct
30	Correct	15 ms	23728 KB	Output is correct
31	Correct	17 ms	23884 KB	Output is correct
32	Correct	15 ms	23812 KB	Output is correct
33	Correct	16 ms	23756 KB	Output is correct
34	Correct	15 ms	23756 KB	Output is correct
35	Correct	16 ms	23736 KB	Output is correct
36	Correct	15 ms	23756 KB	Output is correct
37	Correct	16 ms	23784 KB	Output is correct
38	Correct	16 ms	23888 KB	Output is correct
39	Correct	15 ms	23716 KB	Output is correct
40	Correct	15 ms	23756 KB	Output is correct
41	Correct	16 ms	23732 KB	Output is correct
42	Correct	16 ms	23816 KB	Output is correct
43	Correct	17 ms	23884 KB	Output is correct
44	Correct	15 ms	23752 KB	Output is correct
45	Correct	16 ms	23756 KB	Output is correct
46	Correct	19 ms	23856 KB	Output is correct
47	Correct	15 ms	23756 KB	Output is correct
48	Correct	19 ms	23756 KB	Output is correct
49	Correct	16 ms	23884 KB	Output is correct
50	Correct	15 ms	23828 KB	Output is correct
51	Correct	15 ms	23756 KB	Output is correct
52	Correct	15 ms	23756 KB	Output is correct
53	Correct	16 ms	23884 KB	Output is correct
54	Correct	16 ms	23756 KB	Output is correct
55	Correct	16 ms	23756 KB	Output is correct
56	Correct	15 ms	23756 KB	Output is correct
57	Correct	16 ms	23844 KB	Output is correct
58	Correct	20 ms	23884 KB	Output is correct

Subtask #3
37.0 / 37.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	17 ms	23768 KB	Output is correct
2	Correct	18 ms	23756 KB	Output is correct
3	Correct	15 ms	23756 KB	Output is correct
4	Correct	15 ms	23756 KB	Output is correct
5	Correct	15 ms	23756 KB	Output is correct
6	Correct	15 ms	23716 KB	Output is correct
7	Correct	15 ms	23756 KB	Output is correct
8	Correct	15 ms	23756 KB	Output is correct
9	Correct	15 ms	23792 KB	Output is correct
10	Correct	15 ms	23824 KB	Output is correct
11	Correct	15 ms	23820 KB	Output is correct
12	Correct	17 ms	23756 KB	Output is correct
13	Correct	17 ms	23756 KB	Output is correct
14	Correct	15 ms	23756 KB	Output is correct
15	Correct	15 ms	23756 KB	Output is correct
16	Correct	15 ms	23748 KB	Output is correct
17	Correct	15 ms	23756 KB	Output is correct
18	Correct	15 ms	23724 KB	Output is correct
19	Correct	15 ms	23756 KB	Output is correct
20	Correct	15 ms	23884 KB	Output is correct
21	Correct	14 ms	23760 KB	Output is correct
22	Correct	19 ms	23984 KB	Output is correct
23	Correct	19 ms	23972 KB	Output is correct
24	Correct	18 ms	23968 KB	Output is correct
25	Correct	18 ms	23980 KB	Output is correct
26	Correct	17 ms	23848 KB	Output is correct
27	Correct	17 ms	23884 KB	Output is correct
28	Correct	17 ms	23884 KB	Output is correct
29	Correct	17 ms	23848 KB	Output is correct
30	Correct	15 ms	23728 KB	Output is correct
31	Correct	17 ms	23884 KB	Output is correct
32	Correct	15 ms	23812 KB	Output is correct
33	Correct	16 ms	23756 KB	Output is correct
34	Correct	15 ms	23756 KB	Output is correct
35	Correct	16 ms	23736 KB	Output is correct
36	Correct	15 ms	23756 KB	Output is correct
37	Correct	16 ms	23784 KB	Output is correct
38	Correct	16 ms	23888 KB	Output is correct
39	Correct	15 ms	23716 KB	Output is correct
40	Correct	15 ms	23756 KB	Output is correct
41	Correct	16 ms	23732 KB	Output is correct
42	Correct	16 ms	23816 KB	Output is correct
43	Correct	17 ms	23884 KB	Output is correct
44	Correct	15 ms	23752 KB	Output is correct
45	Correct	16 ms	23756 KB	Output is correct
46	Correct	19 ms	23856 KB	Output is correct
47	Correct	15 ms	23756 KB	Output is correct
48	Correct	19 ms	23756 KB	Output is correct
49	Correct	16 ms	23884 KB	Output is correct
50	Correct	15 ms	23828 KB	Output is correct
51	Correct	15 ms	23756 KB	Output is correct
52	Correct	15 ms	23756 KB	Output is correct
53	Correct	16 ms	23884 KB	Output is correct
54	Correct	16 ms	23756 KB	Output is correct
55	Correct	16 ms	23756 KB	Output is correct
56	Correct	15 ms	23756 KB	Output is correct
57	Correct	16 ms	23844 KB	Output is correct
58	Correct	20 ms	23884 KB	Output is correct
59	Correct	890 ms	58848 KB	Output is correct
60	Correct	812 ms	49824 KB	Output is correct
61	Correct	15 ms	23756 KB	Output is correct
62	Correct	14 ms	23756 KB	Output is correct
63	Correct	768 ms	52588 KB	Output is correct
64	Correct	20 ms	24396 KB	Output is correct
65	Correct	33 ms	26188 KB	Output is correct
66	Correct	214 ms	44240 KB	Output is correct
67	Correct	625 ms	64324 KB	Output is correct
68	Correct	667 ms	65552 KB	Output is correct
69	Correct	40 ms	25832 KB	Output is correct
70	Correct	333 ms	43860 KB	Output is correct
71	Correct	1376 ms	91800 KB	Output is correct
72	Correct	1274 ms	87072 KB	Output is correct
73	Correct	169 ms	30592 KB	Output is correct
74	Correct	755 ms	47812 KB	Output is correct
75	Correct	101 ms	29092 KB	Output is correct
76	Correct	993 ms	72200 KB	Output is correct
77	Correct	1052 ms	73508 KB	Output is correct
78	Correct	63 ms	27812 KB	Output is correct
79	Correct	685 ms	61376 KB	Output is correct
80	Correct	20 ms	24140 KB	Output is correct
81	Correct	302 ms	39828 KB	Output is correct
82	Correct	1137 ms	70768 KB	Output is correct
83	Correct	734 ms	47740 KB	Output is correct
84	Correct	768 ms	48320 KB	Output is correct
85	Correct	769 ms	48060 KB	Output is correct
86	Correct	777 ms	50136 KB	Output is correct
87	Correct	781 ms	50220 KB	Output is correct

Submission #394634

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