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	Update graph codes
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/**
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 * File: graph_adjacency_list.java
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 * Created Time: 2023-02-12
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 * Author: Krahets (krahets@163.com)
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 */
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package chapter_graph;
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import java.util.*;
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public class graph_traversal {
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    /* 以顶点 vet 为起点,对图 graph 执行广度优先遍历 */
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    // 采用 GraphAdjList 表示图,以方便获取指定结点的所有邻接结点
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    static List<Vertex> graphBFS(GraphAdjList graph, Vertex startVet) {
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        // 顶点遍历序列
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        List<Vertex> res = new ArrayList<>();
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        // 用于记录顶点是否已被访问
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        Set<Vertex> visited = new HashSet<>() {{ add(startVet); }};
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        // 队列用于实现 BFS
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        Queue<Vertex> que = new LinkedList<>() {{ offer(startVet); }};
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        // 循环直至访问完所有顶点
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        while (!que.isEmpty()) {
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            Vertex vet = que.poll(); // 队首顶点出队
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            res.add(vet);            // 访问该顶点
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            // 遍历该顶点的所有邻接顶点
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            for (Vertex adjVet : graph.adjList.get(vet)) {
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                if (!visited.contains(adjVet)) {
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                    que.offer(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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        }
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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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    /* 输入值列表 vals ,返回顶点列表 vets */
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    static Vertex[] valsToVets(int[] vals) {
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        Vertex[] vets = new Vertex[vals.length];
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        for (int i = 0; i < vals.length; i++) {
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            vets[i] = new Vertex(vals[i]);
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        }
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        return vets;
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    }
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    /* 输入顶点列表 vets ,返回值列表 vals */
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    static List<Integer> vetsToVals(List<Vertex> vets) {
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        List<Integer> vals = new ArrayList<>();
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        for (Vertex vet : vets) {
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            vals.add(vet.val);
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        }
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        return vals;
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    }
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    public static void main(String[] args) {
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        /* 初始化无向图 */
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        Vertex[] v = valsToVets(new int[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 });
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        Vertex[][] edges = { { v[0], v[1] }, { v[0], v[3] }, { v[1], v[2] }, { v[1], v[4] }, 
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                             { v[2], v[5] }, { v[3], v[4] }, { v[3], v[6] }, { v[4], v[5] },
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                             { v[4], v[7] }, { v[5], v[8] }, { v[6], v[7] }, { v[7], v[8] }};
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        GraphAdjList graph = new GraphAdjList(edges);
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        System.out.println("\n初始化后,图为");
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        graph.print();
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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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        System.out.println("\n广度优先遍历(BFS)顶点序列为");
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        System.out.println(vetsToVals(res));
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    }
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}
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