Submission #1129505

#	Time	Username	Problem	Language	Result	Execution time	Memory
1129505		Agageldi	Love Polygon (BOI18_polygon)	C++20	0 / 100	2096 ms	52724 KiB

polygon

/*
ID: agageld1
LANG: C++17
TASK:
*/
#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define N 400005
#define ff first
#define ss second
#define pb push_back
#define sz(s) (int)s.size()
#define rep(c, a, b) for(c = a; c <= b; c++)

//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

ll n, t, answer, cnt;
pair<string,string> s[N];
map <string,int> out, vis;
map <string,string> par;

int main () {
	ios::sync_with_stdio(0);cin.tie(0);
	cin >> n;
	for(int i = 1; i <= n; i++) {
		cin >> s[i].ff >> s[i].ss;
		if(s[i].ff == s[i].ss) continue;
		out[s[i].ss]++;
		par[s[i].ff] = s[i].ss;
	}
	queue <string> q;
	for(int i = 1; i <= n; i++) {
		if(s[i].ff == s[i].ss) continue;
		if(!out[s[i].ff]) {
			out[s[i].ff] = -1;
			q.push(s[i].ff);
		}
	}
	if(n%2) {
		cout << "-1\n";
		return 0;
	}
	while(!q.empty()) {
		string h = q.front();
		q.pop();
		if(par.find(par[par[h]]) != par.end())
			out[par[par[h]]]--;
		if(vis[par[h]]) {
			cout << "-1\n";
			return 0;
		}
		cnt++;
		vis[h] = vis[par[h]] = 1;
		for(int i = 1;i <= n; i++) {
			if(vis[s[i].ss] == 0 && !out[s[i].ss]) {
				q.push(s[i].ss);
				out[s[i].ss] = -1;
			}
			if(vis[s[i].ff] == 0 && !out[s[i].ff]) {
				q.push(s[i].ff);
				out[s[i].ff] = -1;
			}
		}
	}
	cout << cnt << '\n';
}

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