Submission #223173

#	Time	Username	Problem	Language	Result	Execution time	Memory
223173		arnold518	Capital City (JOI20_capital_city)	C++14	100 / 100	1053 ms	38116 KiB

capital_city

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

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int MAXN = 2e5;

int N, K, C[MAXN+10], ans=987654321, num[MAXN+10];
vector<int> adj[MAXN+10];

int sz[MAXN+10], del[MAXN+10];

void getsz(int now, int bef)
{
	sz[now]=1;
	for(int nxt : adj[now])
	{
		if(nxt==bef) continue;
		if(del[nxt]) continue;
		getsz(nxt, now);
		sz[now]+=sz[nxt];
	}
}

int getcen(int now, int bef, int S)
{
	for(int nxt : adj[now])
	{
		if(nxt==bef) continue;
		if(del[nxt]) continue;
		if(sz[nxt]>S/2) return getcen(nxt, now, S);
	}
	return now;
}

int par[MAXN+10], vis[MAXN+10], cvis[MAXN+10];
vector<int> V[MAXN+10];
vector<pii> V2;

void dfs(int now, int bef)
{
	par[now]=bef; vis[now]=0; cvis[C[now]]=0;
	V[C[now]].push_back(now);
	V2.push_back({now, C[now]});
	for(int nxt : adj[now])
	{
		if(nxt==bef) continue;
		if(del[nxt]) continue;
		dfs(nxt, now);
	}
}

void decomp(int now)
{
	getsz(now, now);
	now=getcen(now, now, sz[now]);
	del[now]=true;

	dfs(now, now);
	queue<int> Q;
	Q.push(C[now]);
	cvis[C[now]]=true;
	int cnt=0;

	//printf("CENTROID %d\n", now);

	while(!Q.empty())
	{
		int col=Q.front(); Q.pop(); cnt++;

		for(auto it : V[col])
		{
			int v=it;
			while(!vis[v])
			{
				//printf("%d\n", v);
				vis[v]=true;
				if(!cvis[C[v]])
				{
					cvis[C[v]]=true;
					Q.push(C[v]);
				}
				v=par[v];
			}
		}
	}

	bool flag=true;
	for(auto it : V2) if(cvis[it.second] && V[it.second].size()!=num[it.second]) flag=false;
	if(flag) ans=min(ans, cnt);

	for(auto it : V2) V[it.second].clear();
	V2.clear();

	for(int nxt : adj[now])
	{
		if(del[nxt]) continue;
		decomp(nxt);
	}
}

int main()
{
	int i, j;

	scanf("%d%d", &N, &K);
	for(i=1; i<N; i++)
	{
		int u, v;
		scanf("%d%d", &u, &v);
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	for(i=1; i<=N; i++) scanf("%d", &C[i]), num[C[i]]++;

	decomp(1);
	printf("%d\n", ans-1);
}

Compilation message (stderr)

capital_city.cpp: In function 'void decomp(int)':
capital_city.cpp:91:61: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(auto it : V2) if(cvis[it.second] && V[it.second].size()!=num[it.second]) flag=false;
                                          ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
capital_city.cpp: In function 'int main()':
capital_city.cpp:106:9: warning: unused variable 'j' [-Wunused-variable]
  int i, j;
         ^
capital_city.cpp:108:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &N, &K);
  ~~~~~^~~~~~~~~~~~~~~~
capital_city.cpp:112:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &u, &v);
   ~~~~~^~~~~~~~~~~~~~~~
capital_city.cpp:116:40: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(i=1; i<=N; i++) scanf("%d", &C[i]), num[C[i]]++;
                      ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~

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