59 lines
2.1 KiB
C#
59 lines
2.1 KiB
C#
/**
|
|
* File: graph_bfs.cs
|
|
* Created Time: 2023-03-08
|
|
* Author: hpstory (hpstory1024@163.com)
|
|
*/
|
|
|
|
namespace hello_algo.chapter_graph;
|
|
|
|
public class graph_bfs {
|
|
/* Breadth-first traversal */
|
|
// Use adjacency list to represent the graph, to obtain all adjacent vertices of a specified vertex
|
|
List<Vertex> GraphBFS(GraphAdjList graph, Vertex startVet) {
|
|
// Vertex traversal sequence
|
|
List<Vertex> res = [];
|
|
// Hash set, used to record visited vertices
|
|
HashSet<Vertex> visited = [startVet];
|
|
// Queue used to implement BFS
|
|
Queue<Vertex> que = new();
|
|
que.Enqueue(startVet);
|
|
// Starting from vertex vet, loop until all vertices are visited
|
|
while (que.Count > 0) {
|
|
Vertex vet = que.Dequeue(); // Dequeue the vertex at the head of the queue
|
|
res.Add(vet); // Record visited vertex
|
|
foreach (Vertex adjVet in graph.adjList[vet]) {
|
|
if (visited.Contains(adjVet)) {
|
|
continue; // Skip already visited vertices
|
|
}
|
|
que.Enqueue(adjVet); // Only enqueue unvisited vertices
|
|
visited.Add(adjVet); // Mark the vertex as visited
|
|
}
|
|
}
|
|
|
|
// Return the vertex traversal sequence
|
|
return res;
|
|
}
|
|
|
|
[Test]
|
|
public void Test() {
|
|
/* Initialize undirected graph */
|
|
Vertex[] v = Vertex.ValsToVets([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
|
|
Vertex[][] edges =
|
|
[
|
|
[v[0], v[1]], [v[0], v[3]], [v[1], v[2]],
|
|
[v[1], v[4]], [v[2], v[5]], [v[3], v[4]],
|
|
[v[3], v[6]], [v[4], v[5]], [v[4], v[7]],
|
|
[v[5], v[8]], [v[6], v[7]], [v[7], v[8]]
|
|
];
|
|
|
|
GraphAdjList graph = new(edges);
|
|
Console.WriteLine("\nAfter initialization, the graph is");
|
|
graph.Print();
|
|
|
|
/* Breadth-first traversal */
|
|
List<Vertex> res = GraphBFS(graph, v[0]);
|
|
Console.WriteLine("\nBreadth-first traversal (BFS) vertex sequence is");
|
|
Console.WriteLine(string.Join(" ", Vertex.VetsToVals(res)));
|
|
}
|
|
}
|