Submission #1097379

#	Time	Username	Problem	Language	Result	Execution time	Memory
1097379		Alihan_8	Mergers (JOI19_mergers)	C++17	10 / 100	3054 ms	30928 KiB

mergers

#include <bits/stdc++.h>

using namespace std;

#define pb push_back
#define ar array

struct Dsu{
	vector <int> fa;
	
	Dsu(int n){
		fa.resize(n);
		iota(fa.begin(), fa.end(), 0);
	}
	
	int get(int x){ return x ^ fa[x] ? fa[x] = get(fa[x]) : x; }
	
	bool merge(int u, int v){
		u = get(u), v = get(v);
		
		if ( u == v ) return false;
		
		fa[v] = u;
		
		return true;
	} 
};

signed main(){
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int n, k; cin >> n >> k;
	
	vector <vector<int>> adj(n);
	
	for ( int i = 0; i + 1 < n; i++ ){
		int u, v; cin >> u >> v;
		
		--u, --v;
		
		adj[u].pb(v);
		adj[v].pb(u);
	}
	
	vector <int> s(n);
	
	for ( auto &x: s ){
		cin >> x; --x;
	}
	
	auto check = [&](vector <int> t){
		vector <vector<int>> cnt(n, vector <int> (k));
		
		auto dfs = [&](auto dfs, int u, int p) -> void{
			cnt[u][t[u]] = 1;
			
			for ( auto &v: adj[u] ){
				if ( v != p ){
					dfs(dfs, v, u);
					
					for ( int i = 0; i < k; i++ ){
						cnt[u][i] += cnt[v][i];
					}
				}
			}
		};
		
		dfs(dfs, 0, -1);
		
		int bad = 0;
		
		for ( int u = 0; u < n; u++ ){
			bool flag = true;
			
			for ( int t = 0; t < k; t++ ){
				if ( cnt[u][t] > 0 && cnt[u][t] < cnt[0][t] ){
					flag = false;
				}
			}
			
			bad += flag;
		}
		
		return bad == 1;
	};
	
	vector <ar<int,2>> pa;
	
	for ( int i = 0; i < k; i++ ){
		for ( int j = i + 1; j < k; j++ ) pa.pb({i, j});
	}
	
	int opt = n, m = pa.size();
	
	auto dfs = [&](auto dfs, int p, int cnt, Dsu ds) -> void{
		if ( p == m ){
			vector <int> t(n);
		
			for ( int i = 0; i < n; i++ ) t[i] = ds.get(s[i]);
			
			if ( check(t) ){
				opt = min(opt, cnt);
			}
			
			return;
		}
		
		dfs(dfs, p + 1, cnt, ds);
		
		if ( ds.merge(pa[p][0], pa[p][1]) ){
			dfs(dfs, p + 1, cnt + 1, ds);
		}
	};
	
	Dsu ds(k);
	
	dfs(dfs, 0, 0, ds);
	
	cout << opt;
	
	cout << '\n';
}

• Subtask 1: 10 / 10
• Subtask 2: 0 / 24
• Subtask 3: 0 / 14
• Subtask 4: 0 / 22
• Subtask 5: 0 / 30