Submission #147161

#	Time	Username	Problem	Language	Result	Execution time	Memory
147161		fabjanm	Torrent (COI16_torrent)	C++98	0 / 100	480 ms	48812 KiB

torrent

#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<cstring>

using namespace std;

int a,b,n,mid;

vector<int> sus[300500];
int par[300500];
int kolsus[300500];

int vrijeme[300500];
vector<pair<int,int> >v1;
vector<pair<int,int> >edgevi;

pair<int,int>makni;

void input(){
	cin>>n>>a>>b;
	int br1,br2;
	for(int i=0;i<n-1;i++){
		cin>>br1>>br2;
		sus[br1].push_back(br2);
		sus[br2].push_back(br1);
		kolsus[br1]++;
		kolsus[br2]++;
	}
}

void dfs1(int node, int caca){
	par[node]=caca;
	for(int i=0;i<sus[node].size();i++){
		int x=sus[node][i];
		if(x==caca)continue;
		if((x==edgevi[mid].first && node==edgevi[mid].second) || (node==edgevi[mid].first && x==edgevi[mid].second))continue;
		dfs1(x, node);
	}
}

int dfs2(int node, int caca){
	if(sus[node].size()==1 && node!=a && node!=b)return 1;
	vector<int>v;
	for(int i=0;i<sus[node].size();i++){
		int x=sus[node][i];
		if(x==caca)continue;
		if((x==edgevi[mid].first && node==edgevi[mid].second) || (node==edgevi[mid].first && x==edgevi[mid].second))continue;
		//vrijeme[node]=max(vrijeme[node], dfs2(x, node));
		v.push_back(dfs2(x, node));
	}
	sort(v.rbegin(),v.rend());
	int maxx=v[0];
	for(int i=1;i<v.size();i++){
		if(v[i]+i>maxx)maxx=v[i]+i;
	}
	vrijeme[node]=maxx;
	//int raz=(sus[node].size()-1)-vrijeme[node];
	//if(raz>0)vrijeme[node]+=raz;
	//return vrijeme[node]+1;
	return maxx+1;
}

void dfs3(int node, int caca){
	if(node==b && edgevi.size()==0){
		for(int i=0;i<v1.size();i++)edgevi.push_back(v1[i]);
	}
	
	for(int i=0;i<sus[node].size();i++){
		int x=sus[node][i];
		if(x==caca)continue;
		v1.push_back(make_pair(node,x));
		dfs3(x,node);
		v1.pop_back();
	}
}

int binary(){
	int lo=0;
	int hi=edgevi.size();
	
	
	while(lo<hi){
		mid=(lo+hi)/2;
		dfs1(a,a);
		dfs1(b,b);
		
		//for(int i=1;i<=n;i++)cout<<i<<" "<<par[i]<<endl;
		//cout<<endl<<endl;
		
		dfs2(a,a);
		int av=vrijeme[a];
		dfs2(b,b);
		int bv=vrijeme[b];
		
		//cout<<endl<<endl;
		//for(int i=1;i<=n;i++)cout<<i<<" "<<vrijeme[i]<<endl;
		//cout<<endl<<endl;
		//cout<<mid<<" "<<av<<" "<<bv<<endl;
		
		if(av>bv)hi=mid;
		else lo=mid+1;
	}
	
	int av=0,bv=0;
	mid=lo;
	if(mid<edgevi.size()){
		mid=lo;
		dfs1(a,a);
		dfs2(a,a);
		av=vrijeme[a];
	}
	
	if(mid!=0){
		mid--;
		dfs1(b,b);
		dfs2(b,b);
		bv=vrijeme[b];
	}
	//for(int i=1;i<n;i++)cout<<i<<" "<<vrijeme[i]<<endl;
	
	return max(av,bv);
	
}

void solve(){
	//cout<<endl;
	//dfs1(a,a);
	
	/*for(int i=1;i<=n;i++){
		cout<<i<<" -> ";
		for(int j=0;j<sus[i].size();j++){
			cout<<sus[i][j]<<" ";
		}
		cout<<endl;
	}*/
	
	dfs3(a,a);
	//for(int i=0;i<edgevi.size();i++){
	//	cout<<edgevi[i].first<<" "<<edgevi[i].second<<endl;
	//}
	//cout<<endl;
	cout<<binary();
	//dfs1
}

int main(){
	input();
	solve();
	
	
	
	return 0;
}

Compilation message (stderr)

torrent.cpp: In function 'void dfs1(int, int)':
torrent.cpp:35:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<sus[node].size();i++){
              ~^~~~~~~~~~~~~~~~~
torrent.cpp: In function 'int dfs2(int, int)':
torrent.cpp:46:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<sus[node].size();i++){
              ~^~~~~~~~~~~~~~~~~
torrent.cpp:55:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1;i<v.size();i++){
              ~^~~~~~~~~
torrent.cpp: In function 'void dfs3(int, int)':
torrent.cpp:67:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<v1.size();i++)edgevi.push_back(v1[i]);
               ~^~~~~~~~~~
torrent.cpp:70:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<sus[node].size();i++){
              ~^~~~~~~~~~~~~~~~~
torrent.cpp: In function 'int binary()':
torrent.cpp:108:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if(mid<edgevi.size()){
     ~~~^~~~~~~~~~~~~~

• Subtask 1: 0 / 31
• Subtask 2: 0 / 69