Submission #367751

#	Time	Username	Problem	Language	Result	Execution time	Memory
367751		arnold518	Pastiri (COI20_pastiri)	C++14	100 / 100	897 ms	87380 KiB

pastiri

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

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

const int MAXN = 5e5;
const int MAXK = 5e5;
const int INF = 987654321;

int N, K;
vector<int> adj[MAXN+10];

int P[MAXN+10];

int dep[MAXN+10], par[MAXN+10];
int dp[MAXN+10], dp2[MAXN+10];

void dfs(int now, int bef, int d)
{
	dep[now]=d;
	par[now]=bef;
	dp[now]=INF;
	for(int nxt : adj[now])
	{
		if(nxt==bef) continue;
		dfs(nxt, now, d+1);
		dp[now]=min(dp[now], dp[nxt]+1);
	}
	if(P[now]) dp[now]=0;
}

void dfs2(int now, int bef)
{
	int p=INF;
	for(int i=0; i<adj[now].size(); i++)
	{
		int nxt=adj[now][i];
		if(nxt==bef) continue;
		dp2[nxt]=min(dp2[nxt], p);
		p=min(p, dp[nxt]+1);
	}
	p=INF;
	for(int i=adj[now].size()-1; i>=0; i--)
	{
		int nxt=adj[now][i];
		if(nxt==bef) continue;
		dp2[nxt]=min(dp2[nxt], p);
		p=min(p, dp[nxt]+1);
	}
	for(int nxt : adj[now])
	{
		if(nxt==bef) continue;
		dp2[nxt]=min(dp2[nxt], dp2[now]+1);
	}
	if(P[now])
	{
		for(int nxt : adj[now])
		{
			if(nxt==bef) continue;
			dp2[nxt]=0;
		}
	}
	for(int nxt : adj[now])
	{
		if(nxt==bef) continue;
		dfs2(nxt, now);
	}
}

struct Data
{
	int u, du, dv;
	bool operator < (const Data &p) const
	{
		return du<p.du;
	}
};

int L[MAXN+10];

bool vis[MAXN+10];
int main()
{
	scanf("%d%d", &N, &K);
	for(int i=1; i<N; i++)
	{
		int u, v;
		scanf("%d%d", &u, &v);
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	vector<int> VV;
	for(int i=0; i<K; i++)
	{
		int t;
		scanf("%d", &t);
		VV.push_back(t);
		P[t]=1;
	}

	dfs(1, 1, 1);
	for(int i=1; i<=N; i++) dp2[i]=INF;
	dfs2(1, 1);

	//for(int i=1; i<=N; i++) printf("%d ", dp2[i]); printf("\n");

	priority_queue<Data> PQ;
	for(auto it : VV)
	{
		PQ.push({it, dep[it], dep[it],});
		vis[it]=true;
	}
	vector<int> ans;
	memset(L, -1, sizeof(L));
	while(!PQ.empty())
	{
		Data now=PQ.top(); PQ.pop();
		//printf("PQ %d %d %d %d\n", now.u, now.du, now.dv, L[now.u]);
		if(now.dv-dep[now.u]<=L[now.u]) continue;
		if(now.u==1 || dp2[now.u]<now.dv-dep[par[now.u]])
		{
			ans.push_back(now.u);
			//printf("FIX %d\n", now.u);
			int p=now.u, k=now.dv-dep[now.u];
			for(int i=k-1; i>=0; i--)
			{
				p=par[p];
				//printf("%d %d\n", p, i);
				L[p]=max(L[p], i);
				if(p==1) break;
			}
		}
		else if(!vis[par[now.u]])
		{
			vis[par[now.u]]=true;
			PQ.push({par[now.u], dep[par[now.u]], now.dv});
		}
	}
	printf("%d\n", ans.size());
	for(auto it : ans) printf("%d ", it); printf("\n");
}	

Compilation message (stderr)

pastiri.cpp: In function 'void dfs2(int, int)':
pastiri.cpp:37:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   37 |  for(int i=0; i<adj[now].size(); i++)
      |               ~^~~~~~~~~~~~~~~~
pastiri.cpp: In function 'int main()':
pastiri.cpp:141:11: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wformat=]
  141 |  printf("%d\n", ans.size());
      |          ~^     ~~~~~~~~~~
      |           |             |
      |           int           std::vector<int>::size_type {aka long unsigned int}
      |          %ld
pastiri.cpp:142:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  142 |  for(auto it : ans) printf("%d ", it); printf("\n");
      |  ^~~
pastiri.cpp:142:40: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
  142 |  for(auto it : ans) printf("%d ", it); printf("\n");
      |                                        ^~~~~~
pastiri.cpp:86:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   86 |  scanf("%d%d", &N, &K);
      |  ~~~~~^~~~~~~~~~~~~~~~
pastiri.cpp:90:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   90 |   scanf("%d%d", &u, &v);
      |   ~~~~~^~~~~~~~~~~~~~~~
pastiri.cpp:98:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   98 |   scanf("%d", &t);
      |   ~~~~~^~~~~~~~~~

• Subtask 1: 8 / 8
• Subtask 2: 18 / 18
• Subtask 3: 23 / 23
• Subtask 4: 51 / 51