Submission #834765

#	Time	Username	Problem	Language	Result	Execution time	Memory
834765		NK_	Mergers (JOI19_mergers)	C++17	100 / 100	1304 ms	160724 KiB

mergers

// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>
 
using namespace std;
 
#define nl '\n'
#define pb push_back
#define pf push_front
 
#define mp make_pair
#define f first
#define s second
#define sz(x) int(x.size())
 
template<class T> using V = vector<T>;
using pi = pair<int, int>;
using vi = V<int>;
using vpi = V<pi>;
 
using ll = long long;
using pl = pair<ll, ll>;
using vpl = V<pl>;
using vl = V<ll>;
 
using db = long double;
 
template<class T> using pq = priority_queue<T, V<T>, less<T>>;
 
const int MOD = 1e9 + 7;
const ll INFL = ll(1e17);
const int LG = 19;

int main() {
	cin.tie(0)->sync_with_stdio(0);
  	
	int N, K; cin >> N >> K;

	V<vi> adj(N); for(int i = 0; i < N - 1; i++) {
		int u, v; cin >> u >> v; --u, --v;
		adj[u].pb(v);
		adj[v].pb(u);
	}

	vi A(N); for(auto& x : A) { cin >> x; --x; }

	V<vi> up(N, vi(LG)); vi dep(N);
	function<void(int, int)> gen = [&](int u, int p) {
		up[u][0] = p; dep[u] = (u == p ? 0 : dep[p] + 1);
		for(int i = 1; i < LG; i++) up[u][i] = up[up[u][i-1]][i-1];

		for(auto& v : adj[u]) if (v != p) gen(v, u);
	};
	
	auto jmp = [&](int u, int d) {
		for(int i = 0; i < LG; i++) if ((d >> i) & 1) u = up[u][i];
		return u;
	};

	auto lca = [&](int a, int b) {
		if (dep[a] < dep[b]) swap(a, b);
		a = jmp(a, dep[a] - dep[b]);
		if (a == b) return a;

		for(int i = LG - 1; i >= 0; i--) {
			if (up[a][i] != up[b][i]) a = up[a][i], b = up[b][i];
		}
		return up[a][0];
	};

	gen(0, 0);

	vi L(K, -1); for(int u = 0; u < N; u++) {
		if (L[A[u]] == -1) L[A[u]] = u;
		else L[A[u]] = lca(L[A[u]], u);
	}

	int t = 0; vi U(N), st(N), en(N), VT;
	function<void(int, int)> dfs = [&](int u, int p) {
		U[u] = L[A[u]];
		st[u] = t++;
		for(auto& v : adj[u]) if (v != p) {
			dfs(v, u);
			U[u] = lca(U[u], U[v]);
		}
		en[u] = t - 1;

		if (U[u] == u) VT.pb(u);
	};

	dfs(0, 0);	

	if (sz(VT) == 1) {
		cout << 0 << nl;
		exit(0-0);
	}

	sort(begin(VT), end(VT), [&](int u, int v) {
		return st[u] < st[v];
	});

	vi stk = {-1}; V<vi> ADJ(N);
	for(auto& u : VT) {

		while(stk.back() != -1 && en[stk.back()] < st[u]) stk.pop_back();

		if (stk.back() != -1) {
			ADJ[stk.back()].pb(u);
			ADJ[u].pb(stk.back());
		}
		stk.pb(u);
	}

	int leaves = 0; 
	for(auto& u : VT) if (size(ADJ[u]) == 1) leaves++;

	cout << (leaves + 1) / 2 << nl;

	exit(0-0);
} 	

• Subtask 1: 10 / 10
• Subtask 2: 24 / 24
• Subtask 3: 14 / 14
• Subtask 4: 22 / 22
• Subtask 5: 30 / 30