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/**
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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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/* 广度优先遍历 BFS */
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List<Vertex> graphBFS(GraphAdjList graph, Vertex startVet) {
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// 使用邻接表来表示图，以便获取指定顶点的所有邻接顶点
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// 顶点遍历序列
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List<Vertex> res = [];
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// 哈希表，用于记录已被访问过的顶点
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Set<Vertex> visited = {};
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visited.add(startVet);
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// 队列用于实现 BFS
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Queue<Vertex> que = Queue();
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que.add(startVet);
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// 以顶点 vet 为起点，循环直至访问完所有顶点
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while (que.isNotEmpty) {
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Vertex vet = que.removeFirst(); // 队首顶点出队
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res.add(vet); // 记录访问顶点
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// 遍历该顶点的所有邻接顶点
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for (Vertex adjVet in graph.adjList[vet]!) {
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if (visited.contains(adjVet)) {
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continue; // 跳过已被访问的顶点
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}
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que.add(adjVet); // 只入队未访问的顶点
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visited.add(adjVet); // 标记该顶点已被访问
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}
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}
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// 返回顶点遍历序列
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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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/* 初始化无向图 */
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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("\n初始化后，图为");
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graph.printAdjList();
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/* 广度优先遍历 BFS */
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List<Vertex> res = graphBFS(graph, v[0]);
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print("\n广度优先遍历（BFS）顶点序列为");
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print(Vertex.vetsToVals(res));
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}
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