oj.uz

Submission #107920

# Submission time Handle Problem Language Result Execution time Memory
107920 2019-04-26T09:18:23 Z shash42 Network (BOI15_net) C++11
18 / 100
 2000 ms 24056 KB 
#include<bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define pii pair<int, int>

using namespace std;

const int N=5e5+5;
int n, tmr=0;
vector<int> adj[N], lvlst[N];
vector< pii > ans;
int lv[N], p[N];

struct lvsrt
{
	bool operator()(const int &a, const int &b)
	{
		return lv[a]>lv[b];
	}	
};
void dfs(int u)
{
	for(auto &v: adj[u])
	{
		if(v!=p[u])
		{
			p[v]=u;
			dfs(v);
			lv[u]+=lv[v];
		}
	}
	if(adj[u].size()==1 && u!=1)
	{
		tmr++;
		lv[u]=1;
	}
}
int findg(int u)
{
	//cout << tmr << " finding g: " << u << endl;
	for(auto &v: adj[u])
	{
		if(lv[v]>tmr/2 && p[u]!=v)
		{
			return findg(v);
		}
	}
	return u;
}
void findlvs(int u, int subt)
{
	for(auto &v: adj[u])
	{
		if(v!=p[u])
		{
			p[v]=u;
			findlvs(v, subt);
		}
	}
	if(adj[u].size()==1)
	{
		lvlst[subt].pb(u);
	}
}
int main()
{
	cin >> n;
	for(int i = 1; i < n; i++)
	{
		int u, v;
		cin >> u >> v;
		adj[u].pb(v);
		adj[v].pb(u);
	}
	p[1]=1;	
	dfs(1);
	if(adj[1].size()==1) tmr++;
	int g=findg(1);
//	cout << g;
	sort(adj[g].begin(), adj[g].end(), lvsrt());
	memset(p, 0, n+1);
	int numsubt=adj[g].size();
	for(int i = 0; i < numsubt; i++)
	{
		p[adj[g][i]]=g;
		findlvs(adj[g][i], i);
	}
	int itr;
	for(int i = 0; i < numsubt; i++)
	{
		itr=i+1;
		while(lvlst[i].size())
		{
			if(ans.size()==tmr/2) break;
 			while(!lvlst[itr].size())
			{		
				itr++;
				if(itr==numsubt) itr=i+1;
			}
			if(itr>=numsubt) break;
			ans.pb(mp(lvlst[i].back(), lvlst[itr].back()));
			lvlst[i].pop_back(); lvlst[itr].pop_back();
			itr++;
			if(itr==numsubt) itr=i+1;
		}
	}
	if(tmr%2)
	{
		for(int i = 0; i < numsubt; i++)
		{
			if(lvlst[i].size()) ans.pb(mp(lvlst[i][0], g));
		}
	}
	cout << ans.size() << "\n";
	for(auto &v: ans)
	{
		cout << v.first << " " << v.second << "\n";
	}
}

Compilation message

net.cpp: In function 'int main()':
net.cpp:94:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if(ans.size()==tmr/2) break;
       ~~~~~~~~~~^~~~~~~

Subtask #1
18.0 / 18.0

# Verdict Execution time Memory Grader output
1 Correct 25 ms 23800 KB Output is correct
2 Correct 24 ms 23808 KB Output is correct
3 Correct 25 ms 23928 KB Output is correct
4 Correct 25 ms 23880 KB Output is correct
5 Correct 24 ms 23808 KB Output is correct
6 Correct 27 ms 23808 KB Output is correct
7 Correct 25 ms 23808 KB Output is correct
8 Correct 24 ms 23808 KB Output is correct
9 Correct 26 ms 23808 KB Output is correct
10 Correct 25 ms 23800 KB Output is correct
11 Correct 25 ms 23808 KB Output is correct
12 Correct 24 ms 23928 KB Output is correct
13 Correct 25 ms 23808 KB Output is correct
14 Correct 26 ms 23876 KB Output is correct
15 Correct 24 ms 23808 KB Output is correct
16 Correct 25 ms 23808 KB Output is correct
17 Correct 28 ms 23800 KB Output is correct
18 Correct 30 ms 23808 KB Output is correct
19 Correct 31 ms 23780 KB Output is correct
20 Correct 25 ms 23808 KB Output is correct

Subtask #2
0 / 45.0

# Verdict Execution time Memory Grader output
1 Correct 25 ms 23800 KB Output is correct
2 Correct 24 ms 23808 KB Output is correct
3 Correct 25 ms 23928 KB Output is correct
4 Correct 25 ms 23880 KB Output is correct
5 Correct 24 ms 23808 KB Output is correct
6 Correct 27 ms 23808 KB Output is correct
7 Correct 25 ms 23808 KB Output is correct
8 Correct 24 ms 23808 KB Output is correct
9 Correct 26 ms 23808 KB Output is correct
10 Correct 25 ms 23800 KB Output is correct
11 Correct 25 ms 23808 KB Output is correct
12 Correct 24 ms 23928 KB Output is correct
13 Correct 25 ms 23808 KB Output is correct
14 Correct 26 ms 23876 KB Output is correct
15 Correct 24 ms 23808 KB Output is correct
16 Correct 25 ms 23808 KB Output is correct
17 Correct 28 ms 23800 KB Output is correct
18 Correct 30 ms 23808 KB Output is correct
19 Correct 31 ms 23780 KB Output is correct
20 Correct 25 ms 23808 KB Output is correct
21 Correct 24 ms 23808 KB Output is correct
22 Correct 27 ms 24036 KB Output is correct
23 Correct 27 ms 24056 KB Output is correct
24 Correct 31 ms 24056 KB Output is correct
25 Correct 29 ms 23928 KB Output is correct
26 Correct 31 ms 23928 KB Output is correct
27 Execution timed out 2037 ms 23928 KB Time limit exceeded
28 Halted 0 ms 0 KB -

Subtask #3
0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 25 ms 23800 KB Output is correct
2 Correct 24 ms 23808 KB Output is correct
3 Correct 25 ms 23928 KB Output is correct
4 Correct 25 ms 23880 KB Output is correct
5 Correct 24 ms 23808 KB Output is correct
6 Correct 27 ms 23808 KB Output is correct
7 Correct 25 ms 23808 KB Output is correct
8 Correct 24 ms 23808 KB Output is correct
9 Correct 26 ms 23808 KB Output is correct
10 Correct 25 ms 23800 KB Output is correct
11 Correct 25 ms 23808 KB Output is correct
12 Correct 24 ms 23928 KB Output is correct
13 Correct 25 ms 23808 KB Output is correct
14 Correct 26 ms 23876 KB Output is correct
15 Correct 24 ms 23808 KB Output is correct
16 Correct 25 ms 23808 KB Output is correct
17 Correct 28 ms 23800 KB Output is correct
18 Correct 30 ms 23808 KB Output is correct
19 Correct 31 ms 23780 KB Output is correct
20 Correct 25 ms 23808 KB Output is correct
21 Correct 24 ms 23808 KB Output is correct
22 Correct 27 ms 24036 KB Output is correct
23 Correct 27 ms 24056 KB Output is correct
24 Correct 31 ms 24056 KB Output is correct
25 Correct 29 ms 23928 KB Output is correct
26 Correct 31 ms 23928 KB Output is correct
27 Execution timed out 2037 ms 23928 KB Time limit exceeded
28 Halted 0 ms 0 KB -