Submission #830618

#	Time	Username	Problem	Language	Result	Execution time	Memory
830618		caganyanmaz	Thousands Islands (IOI22_islands)	C++17	22.75 / 100	28 ms	8916 KiB

islands

#include <bits/stdc++.h>
#define mp(x...) array<int, 2>({x})
#define pb push_back
#include "islands.h"
using namespace std;


//#include "../debug.h"
#define debug(x...) void(42)


int n, m;
vector<int> u, v;
variant<bool, vector<int>> subtask1()
{
	if (n <= 2)
		return false;
	array<array<int, 3>, 3> a;
	for (int i = 0; i < m; i++)
		if (u[i] <= 2 && v[i] <= 2)
			a[u[i]][v[i]] = i;	
	debug(a);
	return vector<int>({a[0][1], a[1][2], a[2][0], a[0][2], a[2][1], a[1][0], a[2][0], a[1][2], a[0][1], a[1][0], a[2][1], a[0][2]});
}

constexpr static int MXN = 1e5;

bitset<MXN> visited;
vector<array<int, 2>> g[MXN];

vector<int> res;
bool dfs(int node, int le)
{
	visited[node] = true;
	debug(node, g[node]);
	if (g[node].size() > 2 || (g[node].size() > 1 && le < 0))
	{
		for (auto [c,e] : g[node])
		{
			if (e/2 == le/2)
				continue;
			res.pb(e);
			res.pb(e^1);
		}
		for (auto [c, e] : g[node])
		{
			if (e/2 == le/2)
				continue;
			res.pb(e^1);
			res.pb(e);
		}
		return true;
	}
	for (auto [c, e] : g[node])
	{
		debug(node, c, e, le);
		if (!visited[c])
		{
			res.pb(e);
			if (dfs(c, e))
			{
				res.pb(e);
				return true;
			}
			res.pop_back();
		}
	}
	return false;
}

static inline int get_reverse(int i)
{
	return (i / 2) * 2 + 1 - (i&1);
}

variant<bool, vector<int>> subtask2()
{
	if (dfs(0, -5))
		return res;
	return false;
}

bool dfs2(int node)
{
	visited[node] = true;
	for (auto [c,e]: g[node])
		if (visited[c] || dfs2(c))
			return true;
	return false;
}

variant<bool, vector<int>> subtask3()
{
	return dfs2(0);
}

variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) 
{
	n = N;
	m = M;
	u = U;
	v = V;
	for (int i = 0; i < m; i++)
	{
		g[u[i]].pb(mp(v[i], i));
		debug(i, u[i], v[i]);
	}
	if (u[0] == v[0])
		return subtask3();
	return subtask2();
	assert(false);
}

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