Submission #1280975

#	Time	Username	Problem	Language	Result	Execution time	Memory
1280975		wedonttalkanymore	Mergers (JOI19_mergers)	C++20	100 / 100	533 ms	85028 KiB

mergers

#include <bits/stdc++.h>
/*
    Phia ben kia dai duong cung chi co
    Bo cat nang niu bien thoi
*/
using namespace std;
using ll = long long;

#define int long long
#define pii pair<ll, ll>
#define fi first
#define se second

const ll N = 5e5 + 5, inf = 1e18, mod = 1e9 + 7, block = 320, lim = 19;

int n, k;
vector <int> adj[N], grp[N];

struct DSU {
	int par[N];
	void makeset() {
		for (int i = 1; i <= n; i++) {
			par[i] = i;
		}
	}
	int find(int u) {
		if (par[u] == u) return u;
		return par[u] = find(par[u]);
	}
	void join(int u, int v) {
		u = find(u), v = find(v);
		if (u != v) {
			par[v] = u;
		}
	}
} dsu;

int par[N], depth[N];
int on[N];

void dfs(int u, int parent) {
	par[u] = parent;
	for (auto v : adj[u]) {
		if (v != parent) {
			depth[v] = depth[u] + 1;
			dfs(v, u);
		}
	}
}

void merge(int a, int b) {
	a = dsu.find(a), b = dsu.find(b);
	while(a != b) {
//		cout << a << ' ' << b << ' ' << depth[a] << ' ' << depth[b] << '\n';
		if (depth[a] > depth[b]) swap(a, b);
//		cout << a << ' ' << b << ' ' << depth[a] << ' ' << depth[b] << '\n';
//		cout << "at: " << par[b] << '\n';
		dsu.join(par[b], b);
//		cout << b << ' ' << par[b] << ' ' << dsu.find(par[b]) << dsu.find(2) << '\n';
		b = dsu.find(par[b]);
	}
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    if (fopen(".inp", "r")) {
        freopen(".inp", "r", stdin);
        freopen(".out", "w", stdout);
    }
    cin >> n >> k;
	dsu.makeset();
	for (int i = 1; i < n; i++) {
		int u, v;
		cin >> u >> v;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	dfs(1, 0);
//	for (int i = 1; i <= n; i++) cout << par[i] << ' ';
//	cout << '\n';
//	cout << dsu.find(2) << '\n';
	for (int i = 1; i <= n; i++) {
		int x;
		cin >> x;
		grp[x].push_back(i);
	}
	for (int i = 1; i <= k; i++) {
		if (grp[i].size() < 2) continue;
		for (int j = 1; j < grp[i].size(); j++) {
			merge(grp[i][0], grp[i][j]);
		}
	}
	int ans = 0;
	for (int i = 1; i <= n; i++) {
		for (auto v : adj[i]) {
			int x = dsu.find(i), y = dsu.find(v);
			if (x != y) {
				if (on[x] == 0) ans++;
				else if (on[x] == 1) ans--;
				on[x]++;
			}
		}
	}
	cout << (ans + 1) / 2;
    return 0;
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:68:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   68 |         freopen(".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~
mergers.cpp:69:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   69 |         freopen(".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~

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