Submission #1098738

#	Time	Username	Problem	Language	Result	Execution time	Memory
1098738		vjudge1	Love Polygon (BOI18_polygon)	C++17	46 / 100	2096 ms	15916 KiB

polygon

#include <bits/stdc++.h>

using namespace std;

#define ar array
#define int long long
#define ld long double
#define crash assert(69 == 420)

const int N = 2e5 + 20;
const int MOD = 1e9 + 7;
const int INF = 1e18;
const int X = 100;

int p[N];
int n;

namespace sub1{
	vector<int> g[N];
	bitset<N> vis;
	int cnt = 0;

	void dfs(int x){
		vis[x] = 1;
		cnt++;
		for(auto u: g[x]){
			if(!vis[u])dfs(u);
		}
	}

	bool check(int msk){
		vector<int> v;
		for(int i = 0;i < n;i++){
			if(p[i] == i){
				if((1 << i) & msk){

				}else return 0;
			}
		}
		for(int i = 0;i < n;i++)g[i].clear();
		vis &= 0;
		for(int i = 0;i < n;i++){
			if((1 << i) & msk){

			}else{
				g[i].push_back(p[i]);
				g[p[i]].push_back(i);
			}
		}
		for(int i = 0;i<n;i++){
			if(!vis[i]){
				cnt = 0;
				dfs(i);
				if(cnt > 2)return 0;
			}
		}
		return 1;
	}
};

namespace sub2{
	void solve(){
		int ans = 0;
		bitset<N> vis;
		for(int i = 0;i < n;i++){
			if(vis[i])continue;
			int u = p[i];
			vis[i] = 1;
			int cnt = 1;
			while(u != i){
				vis[u] = 1;
				cnt++;
				u = p[u];
			}
			if(cnt % 2)ans += cnt / 2 + 1;
			else if(cnt > 2)ans += cnt / 2;
		}
		cout<<ans;
	}

};

signed main(){ios_base::sync_with_stdio(false);cin.tie(0);
	//int n;
	cin>>n;
	if(n % 2){
		cout<<-1<<endl;
		return 0;
	}
	map<string, int> mp;
	int G = 0;
	for(int  i = 0;i < n;i++){
		string a, b;
		cin>>a>>b;
		if(!mp.count(a))mp[a] = G++;
		if(!mp.count(b))mp[b] = G++;
		p[mp[a]] = mp[b];
	}
	if(n <= 20){
		int ans = INF;
		for(int i = 0;i < (1 << n);i++){
			if(sub1::check(i))ans = min(ans, (int)__builtin_popcount(i));
		}
		cout<<ans;
		return 0;
	}
	sub2::solve();
}	

• Subtask 1: 21 / 21
• Subtask 2: 25 / 25
• Subtask 3: 0 / 29
• Subtask 4: 0 / 25