Submission #481233

#	Time	Username	Problem	Language	Result	Execution time	Memory
481233		Rainbowbunny	Pastiri (COI20_pastiri)	C++17	100 / 100	981 ms	130884 KiB

pastiri

#include <bits/stdc++.h>
using namespace std;
 
const int MAXN = 5e5 + 5;
const int INF = 1e9;
 
int n, k, tim;
int H[MAXN], d[MAXN], a[MAXN];
int up[MAXN][20], cnt[MAXN];
bool Vis[MAXN];
vector <int> Ans, V;
vector <int> NAdj[MAXN];
vector <int> Adj[MAXN];
 
void DFS(int node, int p = 1)
{
    up[node][0] = p;
    for(int i = 1; i <= 18; i++)
    {
        up[node][i] = up[up[node][i - 1]][i - 1];
    }
    tim++;
    for(auto x : Adj[node])
    {
        if(x == p)
        {
            continue;
        }
        H[x] = H[node] + 1;
        DFS(x, node);
    }
}
 
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
  	Ans.reserve(MAXN);
  	V.reserve(MAXN);
    cin >> n >> k;
    for(int i = 1; i < n; i++)
    {
        int u, v;
        cin >> u >> v;
        Adj[u].push_back(v);
        Adj[v].push_back(u);
    }
    DFS(1);
    for(int i = 1; i <= n; i++)
    {
        d[i] = -1;
    }
    queue <int> BFS;
    for(int i = 1; i <= k; i++)
    {
        cin >> a[i];
        d[a[i]] = 0;
        BFS.push(a[i]);
        V.push_back(a[i]);
    }
    while(BFS.empty() == false)
    {
        int node = BFS.front();
        BFS.pop();
        for(auto x : Adj[node])
        {
            if(d[x] == -1)
            {
                d[x] = d[node] + 1;
                BFS.push(x);
            }
            if(d[x] == d[node] + 1)
            {
                NAdj[x].push_back(node);
            }
        }
    }
    sort(V.begin(), V.end(), [](int x, int y)
    {
        return H[x] > H[y];
    });
    for(auto x : V)
    {
        if(Vis[x])
        {
            continue;
        }
        int cur = x;
        for(int i = 18; i >= 0; i--)
        {
            int nx = up[cur][i];
            if(H[x] - H[nx] <= d[nx])
            {
                cur = nx;
            }
        }
        if(Vis[cur])
        {
            continue;
        }
        Ans.push_back(cur);
        queue <int> q;
        Vis[cur] = true;
        q.push(cur);
        while(q.empty() == false)
        {
            int node = q.front();
            q.pop();
            for(auto y : NAdj[node])
            {
                if(!Vis[y])
                {
                    Vis[y] = true;
                    q.push(y);
                }
            }
        }
    }
    cout << Ans.size() << '\n';
    for(auto x : Ans)
    {
        cout << x << ' ';
    }
    cout << '\n';
}

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