Submission #979070

#	Time	Username	Problem	Language	Result	Execution time	Memory
979070		happy_node	Capital City (JOI20_capital_city)	C++17	0 / 100	2890 ms	524292 KiB

capital_city

#include <bits/stdc++.h>
using namespace std;

const int MX=2e5+5,LOG=18;

int N,K;
int A[MX],B[MX],S[MX];

vector<int> adj[MX], group[MX];

int id[MX][LOG], up[MX][LOG];

int timer=0,tin[MX],tout[MX];

void dfs(int v, int p) {
	tin[v]=++timer;
	up[v][0]=p;
	for(int k=1;k<LOG;k++) up[v][k]=up[up[v][k-1]][k-1];
	for(auto u:adj[v]) {
		if(u==p) continue;
		dfs(u,v);
	}
	tout[v]=timer;
}

bool isAnc(int anc, int v) {
	return tin[anc]<=tin[v] && tout[v]<=tout[anc];
}

int LCA(int u, int v) {
	if(isAnc(u,v)) return u;
	if(isAnc(v,u)) return v;
	for(int k=LOG-1;k>=0;k--) {
		if(up[u][k]!=0 && !isAnc(up[u][k],v)) u=up[u][k];
	}
	return up[u][0];
}

vector<int> scc[MX*LOG], rev[MX*LOG];

vector<int> ord;
bool vis[MX*LOG];

void dfs0(int v) {
	ord.push_back(v);
	vis[v]=true;
	for(auto u:scc[v]) {
		if(!vis[u]) {
			dfs0(u);
		}
	}
}

vector<int> comp;
int cnt[MX*LOG], head[MX*LOG], deg[MX*LOG];

void dfs1(int v) {
	vis[v]=true;
	comp.push_back(v);
	for(auto u:rev[v]) {
		if(!vis[u]) {
			dfs1(u);
		}
	}
}

void add(int v, int anc, int base) {
	for(int k=LOG-2;k>=0;k--) {
		if(up[v][k]!=0 && !isAnc(up[v][k],anc)) {
			assert(id[v][k]!=0);
			scc[base].push_back(id[v][k+1]);
			v=up[v][k];
		}
	}
	scc[base].push_back(id[v][0]);
}

int main() {
	cin.tie(0); ios_base::sync_with_stdio(0);

	cin>>N>>K;
	for(int i=0;i<N-1;i++) {
		cin>>A[i]>>B[i];
		adj[A[i]].push_back(B[i]);
		adj[B[i]].push_back(A[i]);
	}
	for(int i=1;i<=N;i++) {
		cin>>S[i];
		group[S[i]].push_back(i);
	}

	int z=K;
	for(int i=1;i<=N;i++) {
		for(int j=0;j<LOG;j++) {
			id[i][j]=++z;
		}
	}

	dfs(1,0);

	for(int i=1;i<=N;i++) {
		for(int j=1;j<LOG;j++) {
			scc[id[i][j]].push_back(id[i][j-1]);
			if(up[i][j-1]!=0) scc[id[i][j]].push_back(id[up[i][j-1]][j-1]);
		}
		scc[id[i][0]].push_back(S[i]);
	}	

	for(int i=1;i<=K;i++) {
		int cur=group[i][0];
		for(auto x:group[i]) cur=LCA(cur,x);
		for(auto x:group[i]) {
			if(up[x][0]!=0 && !isAnc(up[x][0],cur))
				add(up[x][0],cur,i);
		}
		if(S[cur]!=i) {
			scc[i].push_back(S[cur]);
		}
	}

	for(int i=1;i<=z;i++) {
		for(auto j:scc[i]) {
			rev[j].push_back(i);
		}
	}

	for(int i=1;i<=z;i++) {
		if(vis[i]) continue;
		dfs0(i);
	}

	reverse(ord.begin(),ord.end());
	memset(vis,false,sizeof vis);

	for(auto x:ord) {
		if(vis[x]) continue;
		comp.clear();
		dfs1(x);

		for(auto v:comp) {
			head[v]=comp.front();
			cnt[comp.front()]+=v<=K;
		}
	}

	for(int i=1;i<=z;i++) {
		for(auto j:scc[i]) {
			if(head[i]!=head[j]) {
				deg[head[i]]+=1;
			}
		}
	}

	int ans=K;
	for(int i=1;i<=K;i++) {
		if(deg[head[i]]==0) ans=min(ans,cnt[head[i]]);
	}

	cout<<ans-1<<'\n';
}

• Subtask 1: 0 / 1
• Subtask 2: 0 / 10
• Subtask 3: 0 / 30
• Subtask 4: 0 / 59