142 lines
2.4 KiB
C++
142 lines
2.4 KiB
C++
#include <bits/stdc++.h> // {{{
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// https://codeforces.com/blog/entry/96344
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#pragma GCC optimize("O2,unroll-loops")
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#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
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using namespace std;
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using i32 = int32_t;
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using u32 = uint32_t;
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using i64 = int64_t;
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using u64 = uint64_t;
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using f64 = double;
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using f128 = long double;
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#if __cplusplus >= 202002L
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template <typename T>
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constexpr T MIN = std::numeric_limits<T>::min();
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template <typename T>
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constexpr T MAX = std::numeric_limits<T>::max();
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template <typename T>
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[[nodiscard]] static T sc(auto&& x) {
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return static_cast<T>(x);
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}
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template <typename T>
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[[nodiscard]] static T sz(auto&& x) {
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return static_cast<T>(x.size());
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}
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#endif
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static void NO() {
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std::cout << "NO\n";
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}
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static void YES() {
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std::cout << "YES\n";
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}
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template <typename T>
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using vec = std::vector<T>;
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#define all(x) (x).begin(), (x).end()
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#define rall(x) (x).rbegin(), (x).rend()
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#define ff first
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#define ss second
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#ifdef LOCAL
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#define db(...) std::print(__VA_ARGS__)
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#define dbln(...) std::println(__VA_ARGS__)
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#else
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#define db(...)
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#define dbln(...)
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#endif
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// }}}
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const u32 MAXN = 2 * 1e5 + 1;
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bitset<MAXN> marked, seen;
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vector<vector<u32>> tree(MAXN);
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deque<u32> q;
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void solve() {
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u32 n, k;
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cin >> n >> k;
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marked.reset();
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tree.assign(n + 1, vector<u32>());
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u32 node;
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for (u32 i = 0; i < k; ++i) {
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cin >> node;
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marked[node] = true;
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}
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u32 u, v;
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for (u32 i = 0; i < n - 1; ++i) {
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cin >> u >> v;
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tree[u].emplace_back(v);
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tree[v].emplace_back(u);
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}
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q.clear();
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q.push_back(node);
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seen.reset();
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u32 last = node;
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while (!q.empty()) {
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auto top = q.front();
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q.pop_front();
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seen[top] = true;
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if (marked[top])
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last = top;
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for (auto& neighbor : tree[top]) {
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if (!seen[neighbor]) {
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q.push_back(neighbor);
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}
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}
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}
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q.clear();
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q.push_back(last);
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seen.reset();
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u32 ans = 0, d = 0;
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while (!q.empty()) {
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++d;
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u32 size = q.size();
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for (u32 i = 0; i < size; ++i) {
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auto top = q.front();
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q.pop_front();
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if (marked[top])
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ans = max(ans, d);
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seen[top] = true;
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for (auto& neighbor : tree[top]) {
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if (!seen[neighbor]) {
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q.push_back(neighbor);
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}
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}
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}
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}
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cout << ans / 2 << endl;
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}
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int main() { // {{{
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cin.tie(nullptr)->sync_with_stdio(false);
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cin.exceptions(cin.failbit);
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u32 tc = 1;
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cin >> tc;
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for (u32 t = 0; t < tc; ++t) {
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solve();
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}
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return 0;
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}
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// }}}
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