Submission #156087

#	Time	Username	Problem	Language	Result	Execution time	Memory
156087		HungAnhGoldIBO2020	전압 (JOI14_voltage)	C++14	0 / 100	144 ms	17132 KiB

voltage

#include<iostream>
#include<vector>
#include<algorithm>
const int N=2e5+2;
using namespace std;
vector<int> adj[N];
int cnt[N][3],color[N],level[N],numno=0,ans=0;
vector<pair<int,int> > lis;
bool used[N];
bool dfs(int x,bool valid){
	bool scare=valid,cac;
	for(int i=0;i<adj[x].size();i++){
		if(!color[adj[x][i]]){
			color[adj[x][i]]=3-color[x];
			if(scare){
				scare=dfs(adj[x][i],scare);
			}
			else{
				cac=dfs(adj[x][i],scare);	
			}
		}
		else{
			if(color[adj[x][i]]!=3-color[x]){
				scare=false;
			}
		}
	}
	return scare;
}
void dfs1(int x,int p){
	bool first=true;
	for(int i=0;i<adj[x].size();i++){
		if(!used[adj[x][i]]){
			used[adj[x][i]]=true;
			level[adj[x][i]]=level[x]+1;
			dfs1(adj[x][i],x);
			cnt[x][0]+=cnt[adj[x][i]][0];
			cnt[x][1]+=cnt[adj[x][i]][1];
		}
		else{
			if(level[adj[x][i]]>level[x]){
				continue;
			}
			if(adj[x][i]==p){
				if(first){
					first=false;
					continue;
				}
			}
			if((level[x]-level[adj[x][i]])%2==0){
				numno++;
				cnt[x][0]++;
				cnt[adj[x][i]][0]--;
			}
			else{
				cnt[x][1]++;
				cnt[adj[x][i]][1]--;
			}
		}
	}
}
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	int n,m,i,j,k,root=0,cnt1=0;
	cin>>n>>m;
	for(i=1;i<=m;i++){
		cin>>j>>k;
		lis.push_back({min(j,k),max(j,k)});
		adj[j].push_back(k);
		adj[k].push_back(j);
	}
	sort(lis.begin(),lis.end());
	for(i=1;i<lis.size();i++){
		if(i>0&&lis[i].first==lis[i-1].first&&lis[i].second==lis[i-1].second){
			cnt1++;
			if(i==1){
				cnt1++;
			}
			else{
				if(lis[i-1].first!=lis[i-2].first||lis[i-1].second!=lis[i-2].second){
					cnt1++;
				}
			}
		}
	}
	bool cac;
	for(i=1;i<=n;i++){
		if(!color[i]){
			color[i]=1;
			cac=dfs(i,true);
			if(!cac){
				if(!root){
					root=i;
				}
				else{
					cout<<0;
					return 0;
				}
			}
		}
	}
	if(!root){
		cout<<m-cnt1;
		return 0;
	}
	used[root]=true;
	dfs1(root,root);
	if(numno==1){
		ans++;
	}
	for(i=1;i<=n;i++){
		if(i!=root&&used[i]&&cnt[i][0]==numno&&cnt[i][1]==0){
			ans++;
		}
	}
	cout<<ans;
}

Compilation message (stderr)

voltage.cpp: In function 'bool dfs(int, bool)':
voltage.cpp:12:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<adj[x].size();i++){
              ~^~~~~~~~~~~~~~
voltage.cpp:11:19: warning: variable 'cac' set but not used [-Wunused-but-set-variable]
  bool scare=valid,cac;
                   ^~~
voltage.cpp: In function 'void dfs1(int, int)':
voltage.cpp:32:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<adj[x].size();i++){
              ~^~~~~~~~~~~~~~
voltage.cpp: In function 'int main()':
voltage.cpp:74:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(i=1;i<lis.size();i++){
          ~^~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 35
• Subtask 4: 0 / 45