67 lines
1.9 KiB
Dart
67 lines
1.9 KiB
Dart
/**
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* File: graph_bfs.dart
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* Created Time: 2023-05-15
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* Author: liuyuxin (gvenusleo@gmail.com)
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*/
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import 'dart:collection';
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import '../utils/vertex.dart';
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import 'graph_adjacency_list.dart';
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/* Breadth-first traversal */
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List<Vertex> graphBFS(GraphAdjList graph, Vertex startVet) {
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// Use adjacency list to represent the graph, to obtain all adjacent vertices of a specified vertex
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// Vertex traversal sequence
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List<Vertex> res = [];
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// Hash set, used to record visited vertices
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Set<Vertex> visited = {};
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visited.add(startVet);
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// Queue used to implement BFS
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Queue<Vertex> que = Queue();
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que.add(startVet);
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// Starting from vertex vet, loop until all vertices are visited
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while (que.isNotEmpty) {
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Vertex vet = que.removeFirst(); // Dequeue the vertex at the head of the queue
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res.add(vet); // Record visited vertex
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// Traverse all adjacent vertices of that vertex
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for (Vertex adjVet in graph.adjList[vet]!) {
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if (visited.contains(adjVet)) {
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continue; // Skip already visited vertices
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}
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que.add(adjVet); // Only enqueue unvisited vertices
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visited.add(adjVet); // Mark the vertex as visited
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}
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}
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// Return the vertex traversal sequence
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return res;
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}
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/* Dirver Code */
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void main() {
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/* Initialize undirected graph */
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List<Vertex> v = Vertex.valsToVets([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
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List<List<Vertex>> edges = [
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[v[0], v[1]],
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[v[0], v[3]],
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[v[1], v[2]],
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[v[1], v[4]],
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[v[2], v[5]],
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[v[3], v[4]],
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[v[3], v[6]],
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[v[4], v[5]],
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[v[4], v[7]],
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[v[5], v[8]],
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[v[6], v[7]],
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[v[7], v[8]],
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];
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GraphAdjList graph = GraphAdjList(edges);
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print("\nAfter initialization, the graph is");
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graph.printAdjList();
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/* Breadth-first traversal */
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List<Vertex> res = graphBFS(graph, v[0]);
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print("\nBreadth-first traversal (BFS) vertex sequence is");
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print(Vertex.vetsToVals(res));
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}
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