This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
/*
#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("avx2,fma,bmi,bmi2,sse4.2,popcnt,lzcnt")
*/
#include <bits/stdc++.h>
#define taskname "SHEEP"
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define i64 long long
#define pb push_back
#define ff first
#define ss second
#define isz(x) (int)x.size()
using namespace std;
const int mxN = 2e5 + 5;
const int mod = 1e9 + 7;
const i64 oo = 1e18;
int n, k;
int dis[mxN], par[mxN], dep[mxN];
bool vis[mxN], visbfs[mxN];
vector<int> G[mxN], res, cand;
void dfs(int v, int p) {
par[v] = p;
dep[v] = dep[p] + 1;
for (int u : G[v]) {
if (u == p) continue;
dfs(u, v);
}
}
void bfs(int v, int len) {
vector<int> reset;
queue<pair<int, int>> q;
q.emplace(v, 0); visbfs[v] = true;
while (not q.empty()) {
int v = q.front().ff, cdis = q.front().ss; q.pop();
reset.emplace_back(v);
if (cdis < len) {
for (int u : G[v]) if (!visbfs[u]) {
q.emplace(u, cdis + 1);
visbfs[u] = true;
}
}
else {
vis[v] = false;
}
}
for (int v : reset) visbfs[v] = false;
}
void solve() {
cin >> n >> k;
for (int i = 1; i < n; ++i) {
int u, v;
cin >> u >> v;
G[u].emplace_back(v);
G[v].emplace_back(u);
}
fill(dis + 1, dis + n + 1, -1);
queue<int> q;
for (int i = 1; i <= k; ++i) {
int v; cin >> v;
vis[v] = true;
q.emplace(v); dis[v] = 0;
cand.emplace_back(v);
}
while (not q.empty()) {
int v = q.front(); q.pop();
for (int u : G[v]) {
if (dis[u] == -1) {
dis[u] = dis[v] + 1;
q.emplace(u);
}
}
}
dfs(1, 0);
sort(all(cand), [&](int x, int y) {
return dep[x] > dep[y];
});
for (int v : cand) if (vis[v]) {
// cout << v << endl;
int cur = 0;
while (v != 1 && dis[par[v]] == cur + 1) {
++cur, v = par[v];
}
// cout << "chosen: " << v << " " << endl;
res.emplace_back(v);
bfs(v, dis[v]);
}
cout << isz(res) << "\n";
for (int v : res) cout << v << " ";
cout << "\n";
}
signed main() {
#ifndef CDuongg
if(fopen(taskname".inp", "r"))
assert(freopen(taskname".inp", "r", stdin)), assert(freopen(taskname".out", "w", stdout));
#else
freopen("bai3.inp", "r", stdin);
freopen("bai3.out", "w", stdout);
auto start = chrono::high_resolution_clock::now();
#endif
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int t = 1; //cin >> t;
while(t--) solve();
#ifdef CDuongg
auto end = chrono::high_resolution_clock::now();
cout << "\n"; for(int i = 1; i <= 100; ++i) cout << '=';
cout << "\nExecution time: " << chrono::duration_cast<chrono::milliseconds> (end - start).count() << "[ms]" << endl;
#endif
}
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