Submission #877209

#	Time	Username	Problem	Language	Result	Execution time	Memory
877209		fryingduc	Pastiri (COI20_pastiri)	C++17	100 / 100	533 ms	95880 KiB

pastiri

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

#ifdef duc_debug
#include "bits/debug.h"
#else 
#define debug(...)     
#endif

#define int long long

const int maxn = 5e5+5;
int n, k, x[maxn];
vector<int> g[maxn];
int d[maxn], h[maxn], choose[maxn], ok[maxn];

void bfs(){
    memset(d, 0x3f3f3f, sizeof(d));
    queue<int> q;
    for(int i = 1; i <= k; ++i){
        d[x[i]] = 0;
        q.push(x[i]);
    }
    while(!q.empty()){
        int u = q.front();
        q.pop();
        for(auto v:g[u]){
            if(d[v] > d[u] + 1){
                d[v] = d[u] + 1;
                q.push(v);
            }
        }
    }
}
void pre_dfs(int u, int prev, int mx, int st){
    if(h[u] + d[u] > mx){
        mx = h[u] + d[u];
        st = u;
    }
    choose[u] = st;
    for(auto v:g[u]){
        if(v == prev) continue;
        h[v] = h[u] + 1;
        pre_dfs(v, u, mx, st);
    }
}
void dfs(int u){
    ok[u] = 1;
    for(auto v:g[u]){
        if(!ok[v] and d[v] + 1 == d[u]) dfs(v);
    }
}

void solve(){
    cin >> n >> k;
    for(int i = 1; i < n; ++i){
        int u, v; cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    for(int i = 1; i <= k; ++i) cin >> x[i];
    bfs();
    pre_dfs(1, 0, 0, 1);
    sort(x + 1, x + k + 1, [](const int &u, const int &v) ->bool{
        return h[u] > h[v];
    });
    vector<int> res;
    for(int i = 1; i <= k; ++i){
        if(!ok[x[i]]){
            res.push_back(choose[x[i]]);
            dfs(choose[x[i]]);
        }
    }
    cout << res.size() << '\n';
    for(auto i:res) cout << i << " ";
}
signed main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int test = 1;
    // cin >> test;
    for(int i = 1; i <= test; i++){
      // cout << "Case " << "#" << i << ": "; 
      solve();
    }

    return 0;
}

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