Submission #220623

#	Time	Username	Problem	Language	Result	Execution time	Memory
220623		atoiz	Mergers (JOI19_mergers)	C++14	100 / 100	786 ms	94388 KiB

mergers

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

const int MAXN = 500007;
int N, K, ans = 0;
int dsu[MAXN], group[MAXN], last[MAXN], val[MAXN], deg[MAXN];
vector<int> adj[MAXN], add[MAXN];

int root(int u) { return (dsu[u] != u ? dsu[u] = root(dsu[u]) : u); }

void dfs(int u, int p)
{
	dsu[u] = u;
	for (int v : add[u]) {
		if (dsu[v]) val[root(v)] -= 2;
	}

	for (int v : adj[u]) if (v != p) {
		dfs(v, u);
		dsu[v] = u;
		val[u] += val[v];
		deg[u] += (val[v] ? deg[v] : 1);
	}

	if (p == 0) ans += (deg[u] == 1);
	else if (!val[u]) ans += (deg[u] + !val[u] == 1);
}

int main()
{
	ios_base::sync_with_stdio(0); cin.tie(0);
	cin >> N >> K;
	for (int i = 0; i < N - 1; ++i) {
		int u, v;
		cin >> u >> v;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	for (int u = 1; u <= N; ++u) {
		cin >> group[u];
		if (last[group[u]]) {
			int v = last[group[u]];
			add[u].push_back(v);
			add[v].push_back(u);
			++val[u], ++val[v];
		}
		last[group[u]] = u;
	}

	if (N == 2) return cout << K - 1 << endl, 0;

	dfs(1, 0);
	// cout << ans << endl;
	cout << (ans + 1) / 2 << endl;
	return 0;
}

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