Submission #386338

#	Time	Username	Problem	Language	Result	Execution time	Memory
386338		kshitij_sodani	Islands (IOI08_islands)	C++14	27 / 100	2068 ms	131072 KiB

islands

//#pragma GCC optimize("Ofast,unroll-loops")
#include <bits/stdc++.h>
using namespace std;
typedef long long llo;
#define mp make_pair
#define pb push_back
#define a first 
#define b second
#define endl '\n'


int n;
vector<pair<int,int>> adj[1000001];
vector<pair<int,int>> adj2[1000001];

int par[1000001];
int find(int no){
	if(par[no]==no){
		return no;
	}
	par[no]=find(par[no]);
	return par[no];
}
llo dp[1000001][2];
pair<llo,llo> cur;
vector<pair<llo,llo>> pp;
vector<pair<llo,llo>> xx;


vector<llo> tt;
void dfs(int no,int par2=-1){
	
	if(no==cur.b){
		pp=xx;
	}
	tt.pb(no);
	for(auto j:adj[no]){
		/*if(j.a==cur.a and no==cur.b){
			continue;
		}
		if(j.a==cur.b and no==cur.a){
			continue;
		}*/
		if(j.a!=par2){
			xx.pb({j.a,j.b});
			dfs(j.a,no);
			xx.pop_back();
		}
	}
}
int vis[1000001];
void dfs2(int no,int par2=-1){
	dp[no][0]=0;
	dp[no][1]=0;
	vector<llo> ss;
	llo su=0;

	for(auto j:adj2[no]){
		if(j.a!=par2){
			dfs2(j.a,no);
	//		dp[no][0]=max(dp[no][0],j.b+dp[j.a][0]);
			su+=dp[j.a][1];
			ss.pb(dp[j.a][0]+j.b-dp[j.a][1]);
		}
	}
	sort(ss.begin(),ss.end());
	reverse(ss.begin(),ss.end());

	dp[no][1]=su;
	dp[no][0]=su;
	for(int i=0;i<ss.size();i++){
		if(i==2){
			break;
		}
		if(i==0){
			if(ss[i]>=0){
				dp[no][0]+=ss[i];
			}
		}
		if(ss[i]>=0){
			dp[no][1]+=ss[i];
		}
	}


	dp[no][1]=max(dp[no][1],dp[no][0]);



}
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cin>>n;
	for(int i=0;i<n;i++){
		par[i]=i;
	}
	vector<pair<pair<int,int>,int>> ed;
	for(int i=0;i<n;i++){
		int aa,cc;
		cin>>aa>>cc;
		aa--;
		int x=find(i);
		int y=find(aa);
		if(x!=y){
			par[x]=y;
			adj[i].pb({aa,cc});
			adj[aa].pb({i,cc});
		}
		else{
			ed.pb({{i,aa},cc});
			//cout<<i<<":"<<aa<<":"<<cc<<endl;
		}
		
	}
	llo ans=0;
	for(auto j:ed){
		cur=j.a;
		llo cost=0;
		tt.clear();
		dfs(j.a.a);
		pp.pb({cur.a,j.b});
		for(auto i:pp){
			vis[i.a]=1;
		}

		for(auto i:tt){
			for(auto k:adj[i]){
				if(vis[k.a]+vis[i]<2){
					adj2[i].pb(k);
				}
			}
		}
		/*for(auto i:tt){
			cout<<i<<",";
		}
		cout<<endl;*/
		llo kk=0;
		for(auto i:pp){
			dfs2(i.a);
			kk+=dp[i.a][1];
			//cout<<i.a<<":"<<1<<endl;
		}
		cost=max(cost,kk);
		int xx=pp.size();

		for(int i=0;i<pp.size();i++){
			int ind=i;
			llo su=0;
			for(int cot=0;cot<xx-1;cot++){
				ind++;
				if(ind==xx){
					ind=0;
				}
				su+=pp[ind].b;
				llo cur2=su;
				cur2+=dp[pp[i].a][0]-dp[pp[i].a][1];
				cur2+=dp[pp[ind].a][0]-dp[pp[ind].a][1];
				cost=max(cost,cur2+kk);
				su-=(dp[pp[ind].a][1]);
			}
		}
		for(auto i:pp){
			vis[i.a]=0;
		}




		ans+=cost;
	
	}
	cout<<ans<<endl;





 
 
	return 0;
}
 

Compilation message (stderr)

islands.cpp: In function 'void dfs2(int, int)':
islands.cpp:71:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   71 |  for(int i=0;i<ss.size();i++){
      |              ~^~~~~~~~~~
islands.cpp: In function 'int main()':
islands.cpp:147:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  147 |   for(int i=0;i<pp.size();i++){
      |               ~^~~~~~~~~~

• Subtask 1: 27 / 33
• Subtask 2: 0 / 3
• Subtask 3: 0 / 4
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10