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// File: graph_adjacency_list.go
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// Created Time: 2023-01-31
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// Author: Reanon (793584285@qq.com)
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package chapter_graph
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import (
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"fmt"
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"strconv"
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"strings"
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)
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/* 顶点类 */
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type vertex struct {
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val int
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}
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/* 构造方法 */
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func newVertex(val int) vertex {
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return vertex{
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val: val,
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}
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}
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/* 基于邻接表实现的无向图类 */
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type graphAdjList struct {
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// 邻接表，使用哈希表来代替链表，以提升删除边、删除顶点的效率
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// 请注意，adjList 中的元素是 Vertex 对象
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adjList map[vertex]map[vertex]struct{}
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}
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/* 构造方法 */
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func newGraphAdjList(edges [][]vertex) *graphAdjList {
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g := &graphAdjList{
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adjList: make(map[vertex]map[vertex]struct{}),
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}
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// 添加所有顶点和边
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for _, edge := range edges {
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g.addVertex(edge[0])
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g.addVertex(edge[1])
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g.addEdge(edge[0], edge[1])
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}
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return g
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}
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/* 获取顶点数量 */
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func (g *graphAdjList) size() int {
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return len(g.adjList)
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}
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/* 添加边 */
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func (g *graphAdjList) addEdge(vet1 vertex, vet2 vertex) {
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_, ok1 := g.adjList[vet1]
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_, ok2 := g.adjList[vet2]
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if !ok1 || !ok2 || vet1 == vet2 {
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panic("error")
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}
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// 添加边 vet1 - vet2, 添加匿名 struct{},
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g.adjList[vet1][vet2] = struct{}{}
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g.adjList[vet2][vet1] = struct{}{}
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}
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/* 删除边 */
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func (g *graphAdjList) removeEdge(vet1 vertex, vet2 vertex) {
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_, ok1 := g.adjList[vet1]
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_, ok2 := g.adjList[vet2]
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if !ok1 || !ok2 || vet1 == vet2 {
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panic("error")
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}
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// 删除边 vet1 - vet2, 借助 delete 来删除 map 中的键
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delete(g.adjList[vet1], vet2)
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delete(g.adjList[vet2], vet1)
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}
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/* 添加顶点 */
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func (g *graphAdjList) addVertex(vet vertex) {
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_, ok := g.adjList[vet]
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if ok {
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return
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}
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// 在邻接表中添加一个新链表
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g.adjList[vet] = make(map[vertex]struct{})
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}
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/* 删除顶点 */
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func (g *graphAdjList) removeVertex(vet vertex) {
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_, ok := g.adjList[vet]
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if !ok {
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panic("error")
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}
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// 在邻接表中删除顶点 vet 对应的链表
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delete(g.adjList, vet)
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// 遍历其它顶点的链表，删除所有包含 vet 的边
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for _, set := range g.adjList {
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// 操作
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delete(set, vet)
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}
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}
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/* 打印邻接表 */
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func (g *graphAdjList) print() {
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var builder strings.Builder
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fmt.Printf("邻接表 = \n")
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for k, v := range g.adjList {
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builder.WriteString("\t\t" + strconv.Itoa(k.val) + ": ")
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for vet := range v {
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builder.WriteString(strconv.Itoa(vet.val) + " ")
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}
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fmt.Println(builder.String())
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builder.Reset()
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}
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}
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