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Submission #546466

# Submission time Handle Problem Language Result Execution time Memory
546466 2022-04-07T15:51:41 Z blue Pipes (CEOI15_pipes) C++17
100 / 100
 1025 ms 12204 KB 
#include <iostream>
#include <vector>
using namespace std;
 
const int mx = 100'000;
 
 
int N, M;
 
struct disjoint_set
{
	int* parent = new int[1+mx];
	int* subtree = new int[1+mx];
 
	disjoint_set()
	{
		for(int i = 1; i <= mx; i++)
		{
			parent[i] = i;
			subtree[i] = 1;
		}
	}
 
	int root(int u)
	{
		if(parent[u] == u) return u;
		else return (parent[u] = root(parent[u]));
	}
 
	bool join(int u, int v)
	{
		u = root(u);
		v = root(v);
		if(u == v) return 0;
 
		if(subtree[u] < subtree[v]) swap(u, v);
		parent[v] = u;
		subtree[u] += subtree[v];
 
		return 1;
	}
};
 
int* lowlink; //yes
 
int* dfsind; //yes
 
int dfscurr;
 
int* paredge; //yes
 
int* degree; //yes
 
int* edgelist[1+mx]; //yes
 
int* eu; //yes
int* ev; //yes
 
 
void dfs(int u)
{
	// cerr << "dfs " << u << '\n';
	// cerr << "paredge = ";
	// for(int i = 1; i <= N; i++) cerr << paredge[i] << ' ';
		// cerr << '\n';
	dfsind[u] = ++dfscurr;
 
	for(int h = 0; h < degree[u]; h++)
	{
		int e = edgelist[u][h];
		if(e == paredge[u]) continue;
 
		int v = eu[e] + ev[e] - u;
 
		if(dfsind[v] == 0)
		{
			// cerr << "edge " << u << " -> " << v << '\n';
			paredge[v] = e;
			dfs(v);
			lowlink[u] = min(lowlink[u], lowlink[v]);
		}
		else
		{
			lowlink[u] = min(lowlink[u], dfsind[v]);
		}
	}
 
	// cerr << "dfs end " << u << " : " << lowlink[u] << ' ' << dfsind[u] << '\n';
	// cerr << "paredge = ";
	// for(int i = 1; i <= N; i++) cerr << paredge[i] << ' ';
	// 	cerr << '\n';
 
	if(lowlink[u] >= dfsind[u] && paredge[u] != 0)
	{
		// cerr << "\n\n";
		// cerr << "paredge " << u << " = " << paredge[u] << '\n';
		// cerr << "bridge detected : ";
		cout << eu[paredge[u]] << ' ' << ev[paredge[u]] << '\n';
		// cerr << "\n\n";
	}
}
 
 
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
 
	cin >> N >> M;
 
	disjoint_set A;
	disjoint_set B;
 
	int ect = 0;
 
 
	eu = new int[2*N + 1];
	ev = new int[2*N + 1];
 
	for(int e = 1; e <= M; e++)
	{
		int u, v;
		cin >> u >> v;
 
		if(A.join(u, v))
		{
			ect++;
			eu[ect] = u;
			ev[ect] = v;
		}
		else if(B.join(u, v))
		{
			ect++;
			eu[ect] = u;
			ev[ect] = v;
		}
	}
 
	delete[] A.parent;
	delete[] A.subtree;
	delete[] B.parent;
	delete[] B.subtree;
 
	degree = new int[1+N];
	for(int i = 1; i <= N; i++) degree[i] = 0;
 
	for(int e = 1; e <= ect; e++)
	{
		degree[eu[e]]++;
		degree[ev[e]]++;
	}
 
	for(int i = 1; i <= N; i++)
	{
		edgelist[i] = new int[degree[i]];
	}
 
	// delete[] degree;
 
 
	int* currind = new int[1+N];
	for(int i = 1; i <= N; i++) currind[i] = -1;
 
	// cerr << "done\n";
 
	for(int e = 1; e <= ect; e++)
	{
		currind[eu[e]]++;
		currind[ev[e]]++;
 
		// cerr << currind[eu[e]] << ' ' << degree[eu[e]] << '\n';
		// cerr << currind[ev[e]] << ' ' << degree[ev[e]] << '\n';
 
		edgelist[eu[e]][currind[eu[e]]] = e;
		edgelist[ev[e]][currind[ev[e]]] = e;
	}
 
	delete[] currind;
 
// cerr << "\n\n\n\n";
 
	paredge = new int[1+N];
	lowlink = new int[1+N];
	dfsind = new int[1+N];
 
	for(int i = 1; i <= N; i++) 
	{
		lowlink[i] = 1'000'000;
		dfsind[i] = 0;
		paredge[i] = 0;
	}
 
	dfscurr = 0;
 
	for(int i = 1; i <= N; i++)
	{
		if(dfsind[i]) continue;
 
		dfs(i);
	}
}

Subtask #1
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 1876 KB Output is correct
2 Correct 1 ms 1876 KB Output is correct

Subtask #2
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 1992 KB Output is correct
2 Correct 4 ms 2004 KB Output is correct

Subtask #3
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 96 ms 2068 KB Output is correct
2 Correct 115 ms 2064 KB Output is correct

Subtask #4
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 159 ms 2164 KB Output is correct
2 Correct 172 ms 2164 KB Output is correct

Subtask #5
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 293 ms 3372 KB Output is correct
2 Correct 225 ms 3136 KB Output is correct

Subtask #6
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 335 ms 8656 KB Output is correct
2 Correct 299 ms 5708 KB Output is correct

Subtask #7
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 496 ms 10032 KB Output is correct
2 Correct 475 ms 7564 KB Output is correct

Subtask #8
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 651 ms 12172 KB Output is correct
2 Correct 632 ms 8080 KB Output is correct

Subtask #9
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 831 ms 12204 KB Output is correct
2 Correct 817 ms 8076 KB Output is correct

Subtask #10
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 1025 ms 11608 KB Output is correct
2 Correct 950 ms 9532 KB Output is correct