Submission #244589

#	Time	Username	Problem	Language	Result	Execution time	Memory
244589		kshitij_sodani	Cat in a tree (BOI17_catinatree)	C++17	100 / 100	964 ms	82396 KiB

catinatree

#include <bits/stdc++.h>
using namespace std;
typedef int64_t llo;
#define mp make_pair
#define pb push_back
#define a first 
#define b second
//#define endl '\n'
 
int n,d;
int ans=0;
set<int> adj[200001];
int vis[200001];
vector<pair<int,int>> cur;
int par[200001];
void dfs(int no,int par2=-1,int levv=0){
	cur.pb({levv,no});
	for(auto j:adj[no]){
		if(j==par2){
			continue;
		}
		dfs(j,no,levv+1);
	}
}
int ss[200001];
void dfs2(int no,int par2=-1,int levv=0){
	ss[no]=1;
	for(auto j:adj[no]){
		if(j==par2){
			continue;
		}
		dfs2(j,no,levv+1);
		ss[no]+=ss[j];
	}
}
int lo=0;
int find(int no,int par2=-1){
	for(auto j:adj[no]){
		if(j==par2){
			continue;
		}
		if(ss[j]>lo/2){
			return find(j,no);
		}
	}
	return no;
}
/*vector<int> mm;
void dfs2(int no,int par=-1,int levv=0){
	vis[no]=1;
	mm.pb(no);
//	if(levv<d){
		for(auto j:adj[no]){
			if(j.b==par){
				continue;
			}
			if(j.a+levv>=d){
				break;
			}
			dfs2(j.b,no,levv+j.a);
		}
//	}
}*/
int cot;
int cot2;
vector<pair<int,int>> dist[200001];
int dist2[200001][20];
int lev[200001];
int ind[200001];
void calc(int no,int par2=-1,int levv=0){
	dist2[no][cot2]=levv;
	dist[cot].pb({levv,no});
	for(auto j:adj[no]){
		if(j==par2){
			continue;
		}
		calc(j,no,levv+1);
	}
}

void dec(int no,int par2=-1,int levv=0){
	if(levv>=20){
		while(true){
			continue;
		}
	}
	dfs2(no);

	lo=ss[no];

	int cen=find(no);
	//cout<<cen<<","<<levv<<endl;
	
	cot=cen;
	cot2=levv;

	lev[cen]=levv;
	par[cen]=par2;

	calc(cen);


	sort(dist[cen].begin(),dist[cen].end());
	ind[cen]=0;
	for(auto j:adj[cen]){
		adj[j].erase(cen);
	}

	for(auto j:adj[cen]){
		dec(j,cen,levv+1);
	}
	adj[cen].clear();

}
int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cin>>n>>d;
	for(int i=1;i<n;i++){
		int aa;
		cin>>aa;
		adj[aa].insert(i);
		adj[i].insert(aa);
	}
	dfs(0);
	sort(cur.begin(),cur.end());
	reverse(cur.begin(),cur.end());
	dec(0);

	for(auto no:cur){
		if(vis[no.b]){
			continue;
		}
		int nn=no.b;
		while(nn!=-1){
			int x=dist2[no.b][lev[nn]];
			while(ind[nn]<dist[nn].size()){
				if(dist[nn][ind[nn]].a+x<d){
					vis[dist[nn][ind[nn]].b]=1;
					ind[nn]+=1;
				}
				else{
					break;
				}
			}
			nn=par[nn];
		}
		ans+=1;

		/*ans+=1;
		dfs2(no.b);
		for(auto j:mm){
			for(auto ll:adj[j]){
				if(ll==)
				if(adj[ll].find(j)!=adj[ll].end()){
					adj[ll].erase(j);
				}
			}
		}
		mm.clear();*/
	}
	cout<<ans<<endl;




	return 0;
}

Compilation message (stderr)

catinatree.cpp: In function 'int main()':
catinatree.cpp:137:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    while(ind[nn]<dist[nn].size()){
          ~~~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 40 / 40
• Subtask 3: 49 / 49