Submission #408896

#	Time	Username	Problem	Language	Result	Execution time	Memory
408896		Jasiekstrz	Islands (IOI08_islands)	C++17	90 / 100	1060 ms	131076 KiB

islands

#include<bits/stdc++.h>
#define fi first
#define se second
using namespace std;
const int N=1e6;
vector<int> e[N+10];
int f[N+10];
int l[N+10];
bitset<N+10> vis_fill;
bitset<N+10> vis_s;
bitset<N+10> on_cycle;
pair<long long,long long> ww[N+10];
vector<int> t;
void dfs_fill(int x)
{
	t.push_back(x);
	vis_fill[x]=true;
	for(auto v:e[x])
	{
		if(!vis_fill[v])
			dfs_fill(v);
	}
	return;
}
void dfs_tree(int x)
{
	on_cycle[x]=true;
	for(auto v:e[x])
	{
		if(!on_cycle[v])
		{
			dfs_tree(v);
			ww[x].fi=max({ww[x].fi,ww[v].fi,ww[x].se+ww[v].se+(v==f[x] ? l[x]:l[v])});
			ww[x].se=max(ww[x].se,ww[v].se+(v==f[x] ? l[x]:l[v]));
		}
	}
	return;
}
long long solve()
{
	long long ans=0;
	int c;
	for(int i=t[0];true;i=f[i])
	{
		if(vis_s[i])
		{
			c=i;
			break;
		}
		vis_s[i]=true;
	}
	long long l_all=l[c];
	on_cycle[c]=true;
	for(int i=f[c];i!=c;l_all+=l[i],i=f[i])
		on_cycle[i]=true;
	long long mx=0,mn=0;
	int x=c;
	do{
		x=f[x];
		dfs_tree(x);
		ans=max(ans,ww[x].fi);
		ans=max({ans,mx+ww[x].se,mn+ww[x].se});
		mx=max(mx,ww[x].se)+l[x];
		mn=max(mn,ww[x].se+l_all)-l[x];
	}while(x!=c);
	return ans;
}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		int a,b;
		cin>>a>>b;
		f[i]=a;
		l[i]=b;
		e[i].emplace_back(a);
		e[a].emplace_back(i);
	}
	long long ans=0;
	for(int i=1;i<=n;i++)
	{
		if(!vis_fill[i])
		{
			t.clear();
			dfs_fill(i);
			ans+=solve();
		}
	}
	cout<<ans<<"\n";
	return 0;
}

• Subtask 1: 33 / 33
• Subtask 2: 3 / 3
• Subtask 3: 4 / 4
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 0 / 10