Submission #976386

#	Time	Username	Problem	Language	Result	Execution time	Memory
976386		efedmrlr	Pastiri (COI20_pastiri)	C++17	100 / 100	674 ms	95312 KiB

pastiri

// #pragma GCC optimize("O3,Ofast,unroll-loops")
// #pragma GCC target("avx2,bmi,popcnt")
#include <bits/stdc++.h>

#define lli long long int
#define ld long double
#define REP(i, n) for(int i = 0; (i) < (n); (i)++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define pb push_back
#define MP make_pair

using namespace std;

void fastio() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
}

const int N = 5e5 + 5;
const int INF = 1e9 + 500;
const int MOD = 1e9 + 7;
vector<vector<int> > adj(N, vector<int>()), g(N, vector<int>());
vector<int> she;
vector<int> dist(N, -1), dep(N, 0);
vector<int> p(N, 0);
vector<int> vis(N, 0), a(N, 0);
void bfs() {
    queue<int> qu;
    for(auto c : she) {
        dist[c] = 0;
        qu.push(c);
    }
    while(qu.size()) {
        auto cur = qu.front();
        qu.pop();
        for(auto c : adj[cur]) {
            if(dist[c] != -1) continue;
            dist[c] = dist[cur] + 1;
            qu.push(c); 
        }
    }
} 

void dfs(int node, int par) {
    for(auto c : adj[node]) {
        if(c == par) continue;
        dep[c] = dep[node] + 1;
        p[c] = node;
        dfs(c, node);
    }
}
void dfs2(int node) {
    vis[node] = 1;
    for(auto c : g[node]) {
        if(vis[c]) continue;
        dfs2(c);
    }
}
void solve() {
    int n, k;
    cin >> n >> k;
    REP(i, n - 1) {
        int u, v;
        cin >> u >> v;
        adj[u].pb(v);
        adj[v].pb(u);
    }
    she.resize(k);
    REP(i, k) {
        cin >> she[i];
    }
    dfs(1, 0);
    bfs();
    // for(int i = 1; i <= n; i++) {
    //     cout << "i:" << i << " dep:" << dep[i] << " dist:" << dist[i] << "\n";
    // }
    for(auto c : she) {
        int last = c;
        while(last != 1 && dist[last] < dist[p[last]]) {
            last = p[last];
        }
        a[c] = last;
        // cout << "c:" << c << " ac:" << a[c] << "\n";
    }
    for(int i = 1; i <= n; i++) {
        for(int c : adj[i]) {
            if(dist[c] == dist[i] + 1) {
                g[c].pb(i);
            }
        }
    }
    sort(all(she), [](int x, int y) {
        return dep[x] > dep[y];
    });
    vector<int> res;
    for(auto c : she) {
        if(vis[c]) continue;
        res.pb(a[c]);
        dfs2(a[c]);
    }
    cout << res.size() << "\n";
    for(auto c : res) {
        cout << c << " ";
    }
    cout << "\n";
}

signed main() {
    fastio();
    solve();
}

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