Submission #163196

#	Time	Username	Problem	Language	Result	Execution time	Memory
163196		TadijaSebez	우호 조약 체결 (JOI14_friends)	C++11	100 / 100	148 ms	12268 KiB

friends

#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define ll long long
const int N=100050;
bool was[N];
vector<pair<int,int>> edges;
vector<int> E[N];
int p[N];
int Find(int x){ return p[x]==x?x:p[x]=Find(p[x]);}
void Union(int x, int y){ p[Find(x)]=Find(y);}
void DFS(int u, int w)
{
	was[u]=1;
	for(int v:E[u])
	{
		Union(w,v);
		if(!was[v]) DFS(v,w);
	}
}
int cnt[N];
int main()
{
	int n,m;
	scanf("%i %i",&n,&m);
	for(int i=1;i<=n;i++) p[i]=i;
	for(int i=1,u,v;i<=m;i++) scanf("%i %i",&u,&v),E[u].pb(v),edges.pb({u,v});
	for(int i=1;i<=n;i++) if(E[i].size()>1)
	{
		int w=E[i][0];
		for(int v:E[i])
		{
			Union(v,w);
			if(!was[v]) DFS(v,w);
		}
	}
	ll ans=0;
	for(auto e:edges)
	{
		int u,v;tie(u,v)=e;
		if(Find(u)!=Find(v)) ans++;
	}
	for(int i=1;i<=n;i++) cnt[Find(i)]++;
	for(int i=1;i<=n;i++) ans+=(ll)cnt[i]*(cnt[i]-1);
	printf("%lld\n",ans);
	return 0;
}

Compilation message (stderr)

friends.cpp: In function 'int main()':
friends.cpp:25:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%i %i",&n,&m);
  ~~~~~^~~~~~~~~~~~~~~
friends.cpp:27:59: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(int i=1,u,v;i<=m;i++) scanf("%i %i",&u,&v),E[u].pb(v),edges.pb({u,v});
                            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 30 / 30
• Subtask 3: 65 / 65