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/**
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* File: graph_adjacency_list.java
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* Created Time: 2023-01-26
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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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import utils.*;
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/* 基于邻接表实现的无向图类 */
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class GraphAdjList {
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// 邻接表,key:顶点,value:该顶点的所有邻接顶点
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Map<Vertex, List<Vertex>> adjList;
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/* 构造方法 */
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public GraphAdjList(Vertex[][] edges) {
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this.adjList = new HashMap<>();
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// 添加所有顶点和边
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for (Vertex[] edge : edges) {
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addVertex(edge[0]);
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addVertex(edge[1]);
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addEdge(edge[0], edge[1]);
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}
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}
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/* 获取顶点数量 */
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public int size() {
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return adjList.size();
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}
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/* 添加边 */
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public void addEdge(Vertex vet1, Vertex vet2) {
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if (!adjList.containsKey(vet1) || !adjList.containsKey(vet2) || vet1 == vet2)
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throw new IllegalArgumentException();
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// 添加边 vet1 - vet2
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adjList.get(vet1).add(vet2);
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adjList.get(vet2).add(vet1);
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}
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/* 删除边 */
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public void removeEdge(Vertex vet1, Vertex vet2) {
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if (!adjList.containsKey(vet1) || !adjList.containsKey(vet2) || vet1 == vet2)
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throw new IllegalArgumentException();
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// 删除边 vet1 - vet2
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adjList.get(vet1).remove(vet2);
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adjList.get(vet2).remove(vet1);
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}
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/* 添加顶点 */
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public void addVertex(Vertex vet) {
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if (adjList.containsKey(vet))
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return;
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// 在邻接表中添加一个新链表
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adjList.put(vet, new ArrayList<>());
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}
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/* 删除顶点 */
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public void removeVertex(Vertex vet) {
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if (!adjList.containsKey(vet))
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throw new IllegalArgumentException();
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// 在邻接表中删除顶点 vet 对应的链表
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adjList.remove(vet);
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// 遍历其他顶点的链表,删除所有包含 vet 的边
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for (List<Vertex> list : adjList.values()) {
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list.remove(vet);
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}
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}
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/* 打印邻接表 */
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public void print() {
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System.out.println("邻接表 =");
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for (Map.Entry<Vertex, List<Vertex>> pair : adjList.entrySet()) {
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List<Integer> tmp = new ArrayList<>();
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for (Vertex vertex : pair.getValue())
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tmp.add(vertex.val);
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System.out.println(pair.getKey().val + ": " + tmp + ",");
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}
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}
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}
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public class graph_adjacency_list {
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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 = Vertex.valsToVets(new int[] { 1, 3, 2, 5, 4 });
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Vertex[][] edges = { { v[0], v[1] }, { v[0], v[3] }, { v[1], v[2] },
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{ v[2], v[3] }, { v[2], v[4] }, { v[3], v[4] } };
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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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/* 添加边 */
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// 顶点 1, 2 即 v[0], v[2]
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graph.addEdge(v[0], v[2]);
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System.out.println("\n添加边 1-2 后,图为");
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graph.print();
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/* 删除边 */
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// 顶点 1, 3 即 v[0], v[1]
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graph.removeEdge(v[0], v[1]);
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System.out.println("\n删除边 1-3 后,图为");
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graph.print();
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/* 添加顶点 */
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Vertex v5 = new Vertex(6);
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graph.addVertex(v5);
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System.out.println("\n添加顶点 6 后,图为");
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graph.print();
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/* 删除顶点 */
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// 顶点 3 即 v[1]
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graph.removeVertex(v[1]);
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System.out.println("\n删除顶点 3 后,图为");
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graph.print();
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}
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}
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