Submission #1081698

#	Time	Username	Problem	Language	Result	Execution time	Memory
1081698		Elias	Pipes (CEOI15_pipes)	C++17	0 / 100	661 ms	13884 KiB

pipes

#include <bits/stdc++.h>

using namespace std;

int parent[100000];
int depth[100000];
int root[100000];
int union_parent[100000];
vector<vector<int>> children;

int find(int a)
{
	if (union_parent[a] == a)
		return a;
	return union_parent[a] = find(union_parent[a]);
}

bool unite(int a, int b)
{
	a = find(a);
	b = find(b);

	if (a == b)
		return false;

	if (depth[b] > depth[a])
		swap(a, b);

	union_parent[a] = b;
	return true;
}

vector<vector<int>> adj;

int iter = 0;

int dfs_reconstruct(int i, int d, int p, int r)
{
	root[i] = r;
	parent[i] = p;
	depth[i] = d;

	iter++;

	int subtree = 1;

	// assert(iter < 10000);

	for (int c : adj[i])
	{
		if (c == p)
			continue;
		subtree += dfs_reconstruct(c, d + 1, i, r);
	}

	return subtree;
}

signed main()
{
	cin.tie(0);
	ios_base::sync_with_stdio(false);

	int n, m;
	cin >> n >> m;

	children.resize(n);
	adj.resize(n);

	for (int i = 0; i < n; i++)
	{
		parent[i] = root[i] = union_parent[i] = i;
		children[i] = vector<int>{i};
		depth[i] = 1;
	}

	while (m--)
	{
		int a, b;
		cin >> a >> b;

		a--, b--;

		// for (int i = 0; i < n; i++)
		// 	assert(root[i] == root[parent[i]] && root[i] == root[find(i)] && root[i] == root[parent[find(i)]]);

		if (root[a] == root[b])
		{
			// a = find(a);
			// b = find(b);
			
			// while (a != b)
			// {
			// 	// assert(root[a] == root[b]);

			// 	if (depth[a] < depth[b])
			// 		swap(a, b);

			// 	// assert(parent[a] != a);

			// 	unite(a, parent[a]);

			// 	a = find(a);
			// 	b = find(b);
			// }
		}
		else
		{
			if (children[root[a]].size() < children[root[b]].size())
				swap(a, b);

			vector<pair<int, int>> inserts;
			vector<int> new_nodes;

			int roots = 0;

			for (int i : children[root[b]])
			{
				int p = parent[i];

				new_nodes.push_back(i);

				if (i == p) {
					roots++;
					continue;
				}

				inserts.push_back({i, p});
			}

			assert(roots == 1);

			children[root[b]].clear();

			for (auto [a, b] : inserts)
			{
				adj[a].push_back(b);
				adj[b].push_back(a);
			}

			iter = 0;
			assert(dfs_reconstruct(b, depth[a] + 1, a, root[a]) == new_nodes.size());

			for (int node : new_nodes)
			{
				// assert(root[node] == root[a]);
				children[root[a]].push_back(node);
				// if (depth[node] < depth[find(node)])
				// 	union_parent[find(node)] = node;
			}

			for (auto [a, b] : inserts)
			{
				adj[a].clear();
				adj[b].clear();
			}
		}
	}

	for (int i = 0; i < n; i++)
	{
		if (find(i) != find(parent[i]))
			cout << i + 1 << " " << parent[i] + 1 << "\n";
	}
}

Compilation message (stderr)

In file included from /usr/include/c++/10/cassert:44,
                 from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:33,
                 from pipes.cpp:1:
pipes.cpp: In function 'int main()':
pipes.cpp:142:56: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  142 |    assert(dfs_reconstruct(b, depth[a] + 1, a, root[a]) == new_nodes.size());
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
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• Subtask 3: 0 / 10
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