Submission #167518

#	Time	Username	Problem	Language	Result	Execution time	Memory
167518		faremy	Parachute rings (IOI12_rings)	C++14	55 / 100	4033 ms	89656 KiB

rings

#include <algorithm>
#include <vector>
#include <iostream>


const int MAXN = 1e6;
int rings;

std::vector<int> graph[MAXN];
int parent[MAXN];
int ccSize[MAXN];

int candidate = -1;
int part = 0;
int last = -1;
bool isParticular[MAXN];

std::vector<int> listThree;
std::vector<int> listMore;
bool seen[MAXN];
bool adj[MAXN];


void Init(int N_)
{
	rings = N_;
	for (int iRing = 0; iRing < rings; iRing++)
	{
		parent[iRing] = iRing;
		ccSize[iRing] = 1;
	}
}

int find(int node)
{
	if (node != parent[node])
		parent[node] = find(parent[node]);
	return parent[node];
}

void fillLists(int node)
{
	if (seen[node])
		return;
	seen[node] = true;

	if (graph[node].size() == 3)
		listThree.emplace_back(node);
	else if (graph[node].size() > 3)
		listMore.emplace_back(node);
	for (int next : graph[node])
		fillLists(next);
}

int nogood(int node, int root)
{
	if (seen[node])
		return 0;
	seen[node] = true;

	int degOffset = 0;
	for (int next : graph[node])
		if (next == root)
			degOffset++;

	if (graph[node].size() - degOffset == 3)
		return -1;

	int ans = (graph[node].size() - degOffset <= 1);
	for (int next : graph[node])
	{
		int sub = nogood(next, root);
		if (sub == -1)
			return -1;
		ans |= sub;
	}

	return ans;
}

bool iscrit(int node)
{
	if (adj[node])
		return false;
	adj[node] = true;
	std::fill_n(seen, rings, false);
	seen[node] = true;

	for (int start : graph[node])
		if (!seen[start] && nogood(start, node) < 1)
			return false;
	return true;
}

int check(int node)
{
	listThree.clear();
	listMore.clear();
	std::fill_n(seen, rings, false);
	std::fill_n(adj, rings, false);

	fillLists(node);
	if (listThree.empty() && listMore.empty())
		return ccSize[node];

	if (listMore.size() > 1)
	{
		candidate = -2;
		return 0;
	}

	if (listMore.size() == 1)
	{
		if (iscrit(listMore[0]))
			return 1;
		candidate = -2;
		return 0;
	}

	if (listThree.size() > 4)
	{
		candidate = -2;
		return 0;
	}

	if (listThree.size() < 3)
	{
		int ans = 0;
		for (int root : listThree)
		{
			ans += iscrit(root);
			for (int nxt : graph[root])
				ans += iscrit(nxt);
		}

		if (ans == 0)
			candidate = -2;
		return ans;
	}

	int ans = 0;
	for (int root : listThree)
		ans += iscrit(root);

	if (ans == 0)
		candidate = -2;
	return ans;
}

void Link(int A, int B)
{
	if (candidate == -2)
		return;
	int ccA = find(A);
	int ccB = find(B);

	graph[A].emplace_back(B);
	graph[B].emplace_back(A);

	if (ccA == ccB)
	{
		part += !isParticular[ccA];
		isParticular[ccA] = true;
		last = -1;
	}
	else
	{
		if (ccSize[ccA] < ccSize[ccB])
			std::swap(ccA, ccB);
		parent[ccB] = ccA;
		ccSize[ccA] += ccSize[ccB];

		if (isParticular[ccA] && isParticular[ccB])
		{
			part--;
			last = -1;
		}

		isParticular[ccA] |= isParticular[ccB];
		if (graph[A].size() == 3 || graph[A].size() == 4 || graph[B].size() == 3 || graph[B].size() == 4)
		{
			part += !isParticular[ccA];
			isParticular[ccA] = true;
			last = -1;
		}
		else if (graph[A].size() > 4 || graph[B].size() > 4)
		{
			isParticular[ccA] = true;
		}
	}

	if (isParticular[ccA] && candidate != -2)
		candidate = ccA;
}

int CountCritical()
{
	if (candidate == -2)
		return 0;
	if (part == 0)
		return rings;
	if (part > 1)
		return 0;
	//if (last == -1)
		last = check(candidate);
	return last;
}

• Subtask 1: 20 / 20
• Subtask 2: 17 / 17
• Subtask 3: 18 / 18
• Subtask 4: 0 / 14
• Subtask 5: 0 / 31