Submission #924942

#	Time	Username	Problem	Language	Result	Execution time	Memory
924942		Faisal_Saqib	Cat in a tree (BOI17_catinatree)	C++17	51 / 100	1062 ms	115680 KiB

catinatree

#include <iostream>
#include <vector>
#include <bitset>
#include <map>
using namespace std;
const int N=2e5+10;
int n,d;
vector<int> ma[N],vep[N];
int part[N];
int h[N],dist[N],sz[N];
bitset<N> dead;
int cn;
void dfs(int&x,int p=-1)
{
	sz[x]=1;
	for(int&y:ma[x])
	{
		if(y!=p)
		{
			dfs(y,x);
			sz[x]+=sz[y];
		}
	}
}
int find_centriod(int&x,int p=-1)
{
	for(int&y:ma[x])
	{
		if(y!=p and !dead[y] and sz[y]>(cn/2))
		{
			sz[x]-=sz[y];
			sz[y]+=sz[x];
			return find_centriod(y,x);
		}
	}
	return x;
}
map<int,int> dist1[N];
int tlp;
void compute_distance(int&x,int p=-1)
{
	for(int&y:ma[x])
	{
		if(p!=y and !dead[y])
		{
			dist1[tlp][y]=dist1[tlp][x]+1;
			compute_distance(y,x);
		}
	}
}
int solve(int&x)
{
	cn=sz[x];
	int c=find_centriod(x);
	dist1[c][c]=0;
	tlp=c;
	compute_distance(c);
	dead[c]=1;
	for(int&y:ma[c])
		if(!dead[y])
			part[solve(y)]=c;
	return c;
}
void color(int&st)
{
	int x=st;
	while(x>0)
	{
		dist[x]=min(dist[x],dist1[x][st]);	
		x=part[x];
	}
}
int query(int&st)
{
	int x=st;
	int ans=dist[x];
	while(x>0)
	{
		ans=min(ans,dist1[x][st]+dist[x]);
		x=part[x];
	}
	return ans;
}
int main()
{
	cin.tie(0);
	cout.tie(0);
	ios::sync_with_stdio(0);
	cin>>n>>d;
	vep[0].push_back(1);
	int max_h=0;
	for(int i=2;i<=n;i++)
	{
		int p;
		cin>>p;
		p++;
		h[i]=h[p]+1;
		vep[h[i]].push_back(i);
		max_h=max(max_h,h[i]);
		ma[p].push_back(i);
		ma[i].push_back(p);
	}
	int ans=0;
	for(int j=1;j<=n;j++)
		dist[j]=1e9;
	int o_1=1;
	dfs(o_1);
	solve(o_1);
	for(int cur_h=max_h;cur_h>=0;cur_h--)
	{
		for(int&v:vep[cur_h])
		{
			if(query(v)>=d)
			{
				ans++;
				color(v);
			}
		}
	}
	cout<<ans<<'\n';
	return 0;
}

• Subtask 1: 11 / 11
• Subtask 2: 40 / 40
• Subtask 3: 0 / 49