Submission #1264948

#	Time	Username	Problem	Language	Result	Execution time	Memory
1264948		herominhsteve	Logičari (COCI21_logicari)	C++20	110 / 110	124 ms	39868 KiB

Main

#include <bits/stdc++.h>
#define el '\n'
#define FNAME "NAME"
#define allof(x) x.begin(),x.end()
#define allof1(x) x.begin()+1,x.end()
#define mset(x,n) memset(x,(n),sizeof(x))
using namespace std;
const long long MOD = (long long) 1e9+7;
template<class X,class Y> bool minimize(X &a,Y b){ if (a>b) {a=b; return true;} return false;}
template<class X,class Y> bool maximize(X &a,Y b){ if (a<b) {a=b; return true;} return false;}

void setup(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
	if (fopen(FNAME".inp","r")){
		freopen(FNAME".inp","r",stdin);
		freopen(FNAME".out","w",stdout);
	}
}

const int MAXN = 1e5 + 1;
const int INF = 1e9 + 15092007;

int n;
vector<int> graph[MAXN];
vector<pair<int,int>> edges;

void init(){
	cin>>n;
	for (int i=0;i<n;i++){
		int u,v;
		cin>>u>>v;
		edges.emplace_back(u,v);
		graph[u].push_back(v);
		graph[v].push_back(u);
	}
}

namespace SimpleCycle{
	bool check(){
		for (int i=1;i<=n;i++){
			if (graph[i].size() != 2) return false;
		}
		return true;
	}
	void solve(){
		cout<< (n%4 ? -1 : n/2);
		exit(0);
	}
};

namespace Bitmask{
	bitset<21> visited,blueEye;

	void dfs(int u,bool &seen){
		if (seen) return;
		visited[u]=1;
		int cnt = 0;
		for (int v : graph[u]){
			if (blueEye[v]) cnt++;
		}
		if (cnt!=1) {seen=1;return;}
		for (int v : graph[u]){
			if (!visited[v]){
				dfs(v,seen);
			}
		}
	}

	void solve(){
		int MAXMASK = 1<<n;
		int res = MAXMASK;
		for (int mask=1;mask<MAXMASK;mask++){
			int be = __builtin_popcount(mask);
			visited.reset();
			blueEye.reset();
			for (int i=0;i<n;i++){
				if (mask & (1<<i)){
					blueEye[i+1]=1;
				}
			}
			bool check=0;
			dfs(1,check);
			if (!check) minimize(res,be);
		}
		cout<< (res==MAXMASK ? -1 : res);
		exit(0);
	}
};

namespace SubFinal{
	namespace DSU{
		vector<int> parent;
		vector<int> power;
		void make_set(){
			parent.assign(n+1,0);
			power.assign(n+1,1);
			for (int i=1;i<=n;i++){
				parent[i] = i;
				power[i] = 1;
			}
		}
		int find(int u){
			if (u==parent[u]) return u;
			return parent[u] = find(parent[u]);
		}
		bool Union(int u,int v){
			u = find(u);
			v = find(v);
			if (u==v) return false;
			if (power[u] < power[v]) swap(u,v);
			parent[v] = u;
			power[u] += power[v];
			return true;
		}
	};
	
	int root,spe;
	// ! dp[u][colourU][colourRoot][colourPar][colourSpe]
	// ! number of blueEyed logician at u's child
	long long dp[MAXN][2][2][2][2];

	vector<int> adj[MAXN];
	int parent[MAXN];

	void dfs(int u,int pre){
		parent[u] = pre;
		for (int v : adj[u]){
			if (v^pre){
				dfs(v,u);
			}
		}
	}
	
	void initGraph(){
		DSU::make_set();
		for (pair<int,int> x : edges){
			int u,v; tie(u,v) = x;
			if (DSU::find(u) != DSU::find(v)){
				DSU::Union(u,v);
				adj[u].push_back(v);
				adj[v].push_back(u);
			} else{
				root = u;
				spe = v;
			}
		}
	}

	long long cal(int u,int colourU,int cR,int cP,int cS){
		long long &res = dp[u][colourU][cR][cP][cS];
		if (~res) return res;
		bool check=1;
		if (u==root and colourU ^ cR) check=0;
		if (u==spe and colourU ^ cS) check=0;
		if (u==spe and cP and cR) check=0;
		if (!check) return res=INF;

		res = INF;

		long long sum = colourU;
		for (int v : adj[u]){
			if (v==parent[u]) continue;
			sum += cal(v,0,cR,colourU,cS);
		}

		bool cover=0;
		if (cP) cover = 1;
		if (u==root and cS) cover=1;
		if (u==spe and cR) cover=1;

		if (cover) minimize(res,sum);
		else{
			for (int v : adj[u]){
				if (v==parent[u]) continue;
				long long val = sum - cal(v,0,cR,colourU,cS) + cal(v,1,cR,colourU,cS);
				minimize(res,val);
			}
		}
		return res;
	}	

	void solve(){
		initGraph();
		dfs(root,0);
		mset(dp,-1);
		long long res = INF;
		for (int cR:{0,1}) for (int cS:{0,1}) minimize(res,cal(root,cR,cR,0,cS));
		cout<< (res==INF ? -1 : res);
		exit(0);
	}
};

void sol(){
	if (n<=20) Bitmask::solve();
	if (SimpleCycle::check()) SimpleCycle::solve();
	SubFinal::solve();
}

int main(){
    setup();
    init();
    sol();
}

Compilation message (stderr)

Main.cpp: In function 'void setup()':
Main.cpp:16:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |                 freopen(FNAME".inp","r",stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:17:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   17 |                 freopen(FNAME".out","w",stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 40 / 40
• Subtask 4: 50 / 50