Submission #1255492

#	Time	Username	Problem	Language	Result	Execution time	Memory
1255492		mingga	Mergers (JOI19_mergers)	C++20	100 / 100	249 ms	59332 KiB

mergers

// Author: caption_mingle
#include "bits/stdc++.h"

using namespace std;

#define ln "\n"
#define pb push_back
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define ll long long
const int mod = 1e9 + 7;
const int inf = 2e9;
const int N = 5e5 + 7;
int h[N], n, k, a[N], par[N], pre[N], deg[N];
vector<int> g[N];

void dfs(int u, int p) {
	for(int v : g[u]) {
		if(v == p) continue;
		par[v] = u;
		h[v] = h[u] + 1;
		dfs(v, u);
	}
}

struct DSU {
	vector<int> par;
	int n;
	DSU(int n) : n(n) {
		par.resize(n + 1, 0);
		for(int i = 1; i <= n; i++) par[i] = i;
	}
	int find(int u) {
		return u == par[u] ? u : par[u] = find(par[u]);
	}
	void join(int u, int v) {
		u = find(u), v = find(v);
		if(u == v) return;
		if(h[u] > h[v]) swap(u, v);
		par[v] = u;
	}
};

signed main() {
	cin.tie(0) -> sync_with_stdio(0);
	#define task ""
	if(fopen(task ".INP", "r")) {
		freopen(task ".INP", "r", stdin);
		freopen(task ".OUT", "w", stdout);
	}
	cin >> n >> k;
	for(int i = 1; i < n; i++) {
		int u, v; cin >> u >> v;
		g[u].pb(v);
		g[v].pb(u);
	}
	dfs(1, 0);
	DSU d(n);
	for(int i = 1; i <= n; i++) {
		cin >> a[i];
		if(pre[a[i]]) {
			int v = pre[a[i]];
			int u = i;
			while(u != v) {
				if(h[u] < h[v]) swap(u, v);
				d.join(u, par[u]);
				u = d.find(par[u]);
			}
		}
		pre[a[i]] = i;
	}
	for(int i = 1; i <= n; i++) {
		for(int j : g[i]) {
			if(d.find(i) != d.find(j)) deg[d.find(j)]++;
		}
	}
	int ans = 0;
	for(int i = 1; i <= n; i++) {
		ans += (deg[i] == 1);
	}
	cout << (ans + 1) / 2 << ln;
    cerr << "\nTime: " << clock() * 1000 / CLOCKS_PER_SEC;
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:50:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |                 freopen(task ".INP", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
mergers.cpp:51:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |                 freopen(task ".OUT", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

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