Submission #1042481

#	Time	Username	Problem	Language	Result	Execution time	Memory
1042481		yanb	Thousands Islands (IOI22_islands)	C++17	10.85 / 100	24 ms	6748 KiB

islands

#include <bits/stdc++.h>
	
using namespace std;
	
//#define int long long
#define pii pair<int, int>
	
union Ans {
	bool b;
	vector<int> v;
	Ans(bool b) : b(b) {}
	Ans(vector<int> v) : v(v) {}
	~Ans() {}
	Ans(const Ans&) {}
};
	
Ans n2(int n, int M, vector<int> U, vector<int> V) {
	vector<int> u0, u1;
	for (int i = 0; i < M; i++) {
		if (U[i]) u1.push_back(i);
		else u0.push_back(i);
	}
	
	if (u1.size() > 0 && u0.size() > 1) {
		vector<int> ans = {u0[0], u1[0], u0[1], u0[0], u1[0], u0[1]};
		return ans;
	} else {
		return false;
	}
}
	
void dfs(int v, int p, vector<vector<pii>> &g, vector<bool> &uu, vector<int> &ps) {
	if (uu[v]) return;
	uu[v] = 1;
	ps[v] = p;
	for (auto [u, _] : g[v]) {
		dfs(u, v, g, uu, ps);
	}
}
	
Ans undirected(int n, int M, vector<int> U, vector<int> V) {
	vector<vector<pii>> g(n);
	for (int i = 0; i < M; i++) {
		g[U[i]].push_back({V[i], i});
	}
	
	if (g[0].size() > 1) {
		int u = g[0][0].first, v = g[0][1].first;
		if (u == v) {
			vector<int> ans = {g[0][0].second, g[u][0].second, g[0][1].second, 
				g[0][0].second, g[u][0].second, g[0][1].second};
			return ans;
		}
		return true;
	}
	
	vector<bool> uu(n);
	vector<int> p(n);
	dfs(0, 0, g, uu, p);
	for (int i = 0; i < n; i++) {
		if (g[i].size() > 2 && uu[i]) return true;
	}
	
	return false;
}
	
Ans find_journey(int n, int M, vector<int> U, vector<int> V) {
	if (n == 2) return n2(n, M, U, V);
	return undirected(n, M, U, V);
}
	
#ifdef ONLINE_JUDGE
signed main() {
	Ans ans = find_journey(3, 4, {0, 1, 1, 0}, {1, 0, 0, 1});
	if (ans.b) {
		for (int x : ans.v) cout << x << " ";
		cout << "\n";
	}
}
#endif

• Subtask 1: 1.75 / 5
• Subtask 2: 1.75 / 5
• Subtask 3: 7.35 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 45