Submission #1265857

#	Time	Username	Problem	Language	Result	Execution time	Memory
1265857		mingga	Capital City (JOI20_capital_city)	C++20	100 / 100	533 ms	41376 KiB

capital_city

// 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 = 2e5 + 7;
int n, k, a[N], sz[N], par[N], del[N], dsu[N], rep[N], h[N];
int ans = inf;
bool mark[N], vis[N];
vector<int> col[N], g[N];

vector<int> nodes;

int find(int u) {
	if(dsu[u] < 0) return u;
	return dsu[u] = find(dsu[u]);
}

void join(int u, int v) {
	u = find(u), v = find(v);
	if(u == v) return;
	if(dsu[u] > dsu[v]) swap(u, v);
	rep[u] = (h[rep[u]] < h[rep[v]]) ? rep[u] : rep[v];
	dsu[u] += dsu[v];
	dsu[v] = u;
}

void count(int u, int p) {
	sz[u] = 1;
	for(int v : g[u]) {
		if(v == p or del[v]) continue;
		count(v, u);
		sz[u] += sz[v];
	}
}

int find_cen(int u, int p, int n) {
	for(int v : g[u]) {
		if(del[v] or v == p) continue;
		if(sz[v] * 2 > n) {
			return find_cen(v, u, n);
		}
	}
	return u;
}

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

void solve(int u) {
	count(u, 0);
	int root = find_cen(u, 0, sz[u]);
	dfs(root, 0);
	for(int x : nodes) {
		dsu[x] = -1;
		rep[x] = x;
	}
	bool ok = 1;
	queue<int> q;
	q.push(a[root]);
	vis[a[root]] = 1;
	int cur = 0;
	while(sz(q)) {
		int c = q.front(); q.pop();
		int pre = col[c][0];
		cur++;
		if(!mark[pre]) {
			ok = 0;
			break;
		}
		for(int i = 1; i < sz(col[c]); i++) {
			int u = col[c][i];
			if(!mark[u]) {
				ok = 0;
				break;
			}
			// cerr << u << ' ' << pre << ' ' << rep[u] << ' ' << rep[pre] << ln;
			while(u != pre) {
				// cerr << u << ' ' << pre << ' ' << h[u] << ' ' << h[pre] << ln;
				if(h[u] > h[pre]) {
					join(u, par[u]);
					u = rep[find(u)];
					if(!vis[a[u]]) {
						q.push(a[u]);
						vis[a[u]] = 1;
					}
				} else {
					join(pre, par[pre]);
					pre = rep[find(pre)];
					if(!vis[a[pre]]) {
						q.push(a[pre]);
						vis[a[pre]] = 1;
					}
				}
			}
		}
		if(!ok) break;
	}
	if(ok) {
		ans = min(ans, cur - 1);
		// cerr << "OK " << ln;
		// for(int x : nodes) {
		// 	cerr << x << ' ';
		// }
		// cerr << cur << ln;
	}
	for(int x : nodes) {
		mark[x] = 0;
		vis[a[x]] = 0;
	}
	nodes.clear();
	del[root] = 1;
	for(int v : g[root]) {
		if(del[v]) continue;
		solve(v);
	}
}

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);
	}
	for(int i = 1; i <= n; i++) {
		cin >> a[i];
		col[a[i]].pb(i);
	}
	solve(1);
	cout << ans << ln;
    cerr << "\nTime: " << clock() * 1000 / CLOCKS_PER_SEC;
}

Compilation message (stderr)

capital_city.cpp: In function 'int main()':
capital_city.cpp:140:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  140 |                 freopen(task ".INP", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
capital_city.cpp:141:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  141 |                 freopen(task ".OUT", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 1 / 1
• Subtask 2: 10 / 10
• Subtask 3: 30 / 30
• Subtask 4: 59 / 59