Submission #374681

#	Time	Username	Problem	Language	Result	Execution time	Memory
374681		morato	Love Polygon (BOI18_polygon)	C++17	25 / 100	396 ms	29164 KiB

polygon

#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 5;

map<string, int> id;
string a[N], b[N];
vector<int> adj[N];
int prv[N], ans = 0, vis[N];

void dfs(int v) {
	vis[v] = 1;
	for (int u : adj[v]) {
		if (!vis[u]) {
			prv[u] = v;
			dfs(u);
		} else if (vis[u] == 1) {
			// cout << v << " -> " << u << '\n';
			// cout << "ciclo: " << v << ' ';
			int sz = 1, cur = v;
			while (cur != u) {
				cur = prv[cur];
				sz++;
				// cout << cur << ' ';
			}
			// cout << '\n';
			ans += (sz == 2 ? 0 : (sz + 1) / 2);
		}
	}
	vis[v] = 2;
}

int main() {
	int n; cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> a[i] >> b[i];
		id[a[i]], id[b[i]];
	}
	if (n & 1) {
		cout << -1 << '\n';
		return 0;
	}
	int cnt = 0;
	for (auto it = id.begin(); it != id.end(); it++) {
		it->second = ++cnt;
	}
	for (int i = 0; i < n; i++) {
		adj[id[a[i]]].push_back(id[b[i]]);
	}
	for (int i = 1; i <= n; i++) {
		if (!vis[i]) {
			dfs(i);
		}	
	}
	cout << ans << '\n';
}

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