feat(go/graph): add go code for graph_dfs/bfs (krahets#372)

* feat(vertex): add a vertex pkg

* feat(graph): add graph_bfs in go

* feat(graph): add graph_dfs in go

* fix(graph): fix comment

* fix(graph): fix graph_adj_list

* fix(go/graph): fix graph_adjacency

* fix(c): gitignore

* feat(graph): print order adjList graph

* fix(graph): remove order print

* Update graph_adjacency_list_test.go

* Update .gitignore

* Update .gitignore

---------

Co-authored-by: Yudong Jin <[email protected]>

.gitignore

@@ -3,7 +3,7 @@
 
 # Editor
 .vscode/
-.idea/
+**/.idea
 
 # mkdocs files
 .cache/
@@ -13,3 +13,4 @@ docs/overrides/
 build/
 site/
 utils/
+**/cmake-build-debug

codes/go/chapter_graph/graph_adjacency_list.go

@@ -8,31 +8,20 @@ import (
 	"fmt"
 	"strconv"
 	"strings"
-)
-
-/* 顶点类 */
-type vertex struct {
-	val int
-}
 
-/* 构造方法 */
-func newVertex(val int) vertex {
-	return vertex{
-		val: val,
-	}
-}
+	. "github.com/krahets/hello-algo/pkg"
+)
 
 /* 基于邻接表实现的无向图类 */
 type graphAdjList struct {
-	// 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
-	// 请注意，adjList 中的元素是 Vertex 对象
-	adjList map[vertex]map[vertex]struct{}
+	// 邻接表，key: 顶点，value：该顶点的所有邻接顶点
+	adjList map[Vertex][]Vertex
 }
 
 /* 构造方法 */
-func newGraphAdjList(edges [][]vertex) *graphAdjList {
+func newGraphAdjList(edges [][]Vertex) *graphAdjList {
 	g := &graphAdjList{
-		adjList: make(map[vertex]map[vertex]struct{}),
+		adjList: make(map[Vertex][]Vertex),
 	}
 	// 添加所有顶点和边
 	for _, edge := range edges {
@@ -49,62 +38,62 @@ func (g *graphAdjList) size() int {
 }
 
 /* 添加边 */
-func (g *graphAdjList) addEdge(vet1 vertex, vet2 vertex) {
+func (g *graphAdjList) addEdge(vet1 Vertex, vet2 Vertex) {
 	_, ok1 := g.adjList[vet1]
 	_, ok2 := g.adjList[vet2]
 	if !ok1 || !ok2 || vet1 == vet2 {
 		panic("error")
 	}
 	// 添加边 vet1 - vet2, 添加匿名 struct{},
-	g.adjList[vet1][vet2] = struct{}{}
-	g.adjList[vet2][vet1] = struct{}{}
+	g.adjList[vet1] = append(g.adjList[vet1], vet2)
+	g.adjList[vet2] = append(g.adjList[vet2], vet1)
 }
 
 /* 删除边 */
-func (g *graphAdjList) removeEdge(vet1 vertex, vet2 vertex) {
+func (g *graphAdjList) removeEdge(vet1 Vertex, vet2 Vertex) {
 	_, ok1 := g.adjList[vet1]
 	_, ok2 := g.adjList[vet2]
 	if !ok1 || !ok2 || vet1 == vet2 {
 		panic("error")
 	}
-	// 删除边 vet1 - vet2, 借助 delete 来删除 map 中的键
-	delete(g.adjList[vet1], vet2)
-	delete(g.adjList[vet2], vet1)
+	// 删除边 vet1 - vet2
+	DeleteSliceElms(g.adjList[vet1], vet2)
+	DeleteSliceElms(g.adjList[vet2], vet1)
 }
 
 /* 添加顶点 */
-func (g *graphAdjList) addVertex(vet vertex) {
+func (g *graphAdjList) addVertex(vet Vertex) {
 	_, ok := g.adjList[vet]
 	if ok {
 		return
 	}
 	// 在邻接表中添加一个新链表
-	g.adjList[vet] = make(map[vertex]struct{})
+	g.adjList[vet] = make([]Vertex, 0)
 }
 
 /* 删除顶点 */
-func (g *graphAdjList) removeVertex(vet vertex) {
+func (g *graphAdjList) removeVertex(vet Vertex) {
 	_, ok := g.adjList[vet]
 	if !ok {
 		panic("error")
 	}
 	// 在邻接表中删除顶点 vet 对应的链表
 	delete(g.adjList, vet)
 	// 遍历其它顶点的链表，删除所有包含 vet 的边
-	for _, set := range g.adjList {
-		// 操作
-		delete(set, vet)
+	for _, list := range g.adjList {
+		DeleteSliceElms(list, vet)
 	}
 }
 
 /* 打印邻接表 */
 func (g *graphAdjList) print() {
 	var builder strings.Builder
 	fmt.Printf("邻接表 = \n")
+	// 使邻接表有序输出
 	for k, v := range g.adjList {
-		builder.WriteString("\t\t" + strconv.Itoa(k.val) + ": ")
-		for vet := range v {
-			builder.WriteString(strconv.Itoa(vet.val) + " ")
+		builder.WriteString("\t\t" + strconv.Itoa(k.Val) + ": ")
+		for _, vet := range v {
+			builder.WriteString(strconv.Itoa(vet.Val) + " ")
 		}
 		fmt.Println(builder.String())
 		builder.Reset()

codes/go/chapter_graph/graph_adjacency_list_test.go

@@ -7,41 +7,39 @@ package chapter_graph
 import (
 	"fmt"
 	"testing"
+
+	. "github.com/krahets/hello-algo/pkg"
 )
 
 func TestGraphAdjList(t *testing.T) {
 	/* 初始化无向图 */
-	v0 := newVertex(1)
-	v1 := newVertex(3)
-	v2 := newVertex(2)
-	v3 := newVertex(5)
-	v4 := newVertex(4)
-	edges := [][]vertex{{v0, v1}, {v1, v2}, {v2, v3}, {v0, v3}, {v2, v4}, {v3, v4}}
+	v := ValsToVets([]int{1, 3, 2, 5, 4})
+	edges := [][]Vertex{{v[0], v[1]}, {v[0], v[3]}, {v[1], v[2]}, {v[2], v[3]}, {v[2], v[4]}, {v[3], v[4]}}
 	graph := newGraphAdjList(edges)
 	fmt.Println("初始化后，图为:")
 	graph.print()
 
 	/* 添加边 */
-	// 顶点 1, 2 即 v0, v2
-	graph.addEdge(v0, v2)
+	// 顶点 1, 2 即 v[0], v[2]
+	graph.addEdge(v[0], v[2])
 	fmt.Println("\n添加边 1-2 后，图为")
 	graph.print()
 
 	/* 删除边 */
-	// 顶点 1, 3 即 v0, v1
-	graph.removeEdge(v0, v1)
+	// 顶点 1, 3 即 v[0], v[1]
+	graph.removeEdge(v[0], v[1])
 	fmt.Println("\n删除边 1-3 后，图为")
 	graph.print()
 
 	/* 添加顶点 */
-	v5 := newVertex(6)
+	v5 := NewVertex(6)
 	graph.addVertex(v5)
 	fmt.Println("\n添加顶点 6 后，图为")
 	graph.print()
 
 	/* 删除顶点 */
-	// 顶点 3 即 v1
-	graph.removeVertex(v1)
+	// 顶点 3 即 v[1]
+	graph.removeVertex(v[1])
 	fmt.Println("\n删除顶点 3 后，图为")
 	graph.print()
 }

codes/go/chapter_graph/graph_bfs.go

@@ -0,0 +1,41 @@
+// File: graph_bfs.go
+// Created Time: 2023-02-18
+// Author: Reanon ([email protected])
+
+package chapter_graph
+
+import (
+	. "github.com/krahets/hello-algo/pkg"
+)
+
+/* 广度优先遍历 BFS */
+// 使用邻接表来表示图，以便获取指定顶点的所有邻接顶点
+func graphBFS(g *graphAdjList, startVet Vertex) []Vertex {
+	// 顶点遍历序列
+	res := make([]Vertex, 0)
+	// 哈希表，用于记录已被访问过的顶点
+	visited := make(map[Vertex]struct{})
+	visited[startVet] = struct{}{}
+	// 队列用于实现 BFS, 使用切片模拟队列
+	queue := make([]Vertex, 0)
+	queue = append(queue, startVet)
+	// 以顶点 vet 为起点，循环直至访问完所有顶点
+	for len(queue) > 0 {
+		// 队首顶点出队
+		vet := queue[0]
+		queue = queue[1:]
+		// 记录访问顶点
+		res = append(res, vet)
+		// 遍历该顶点的所有邻接顶点
+		for _, adjVet := range g.adjList[vet] {
+			_, isExist := visited[adjVet]
+			// 只入队未访问的顶点
+			if !isExist {
+				queue = append(queue, adjVet)
+				visited[adjVet] = struct{}{}
+			}
+		}
+	}
+	// 返回顶点遍历序列
+	return res
+}

codes/go/chapter_graph/graph_bfs_test.go

@@ -0,0 +1,29 @@
+// File: graph_bfs_test.go
+// Created Time: 2023-02-18
+// Author: Reanon ([email protected])
+
+package chapter_graph
+
+import (
+	"fmt"
+	"testing"
+
+	. "github.com/krahets/hello-algo/pkg"
+)
+
+func TestGraphBFS(t *testing.T) {
+	/* 初始化无向图 */
+	vets := ValsToVets([]int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9})
+	edges := [][]Vertex{
+		{vets[0], vets[1]}, {vets[0], vets[3]}, {vets[1], vets[2]}, {vets[1], vets[4]},
+		{vets[2], vets[5]}, {vets[3], vets[4]}, {vets[3], vets[6]}, {vets[4], vets[5]},
+		{vets[4], vets[7]}, {vets[5], vets[8]}, {vets[6], vets[7]}, {vets[7], vets[8]}}
+	graph := newGraphAdjList(edges)
+	fmt.Println("初始化后，图为:")
+	graph.print()
+
+	/* 广度优先遍历 BFS */
+	res := graphBFS(graph, vets[0])
+	fmt.Println("广度优先遍历（BFS）顶点序列为:")
+	PrintSlice(VetsToVals(res))
+}

codes/go/chapter_graph/graph_dfs.go

@@ -0,0 +1,36 @@
+// File: graph_dfs.go
+// Created Time: 2023-02-18
+// Author: Reanon ([email protected])
+
+package chapter_graph
+
+import (
+	. "github.com/krahets/hello-algo/pkg"
+)
+
+/* 深度优先遍历 DFS 辅助函数 */
+func dfs(g *graphAdjList, visited map[Vertex]struct{}, res *[]Vertex, vet Vertex) {
+	// append 操作会返回新的的引用，必须让原引用重新赋值为新slice的引用
+	*res = append(*res, vet)
+	visited[vet] = struct{}{}
+	// 遍历该顶点的所有邻接顶点
+	for _, adjVet := range g.adjList[vet] {
+		_, isExist := visited[adjVet]
+		// 递归访问邻接顶点
+		if !isExist {
+			dfs(g, visited, res, adjVet)
+		}
+	}
+}
+
+/* 深度优先遍历 DFS */
+// 使用邻接表来表示图，以便获取指定顶点的所有邻接顶点
+func graphDFS(g *graphAdjList, startVet Vertex) []Vertex {
+	// 顶点遍历序列
+	res := make([]Vertex, 0)
+	// 哈希表，用于记录已被访问过的顶点
+	visited := make(map[Vertex]struct{})
+	dfs(g, visited, &res, startVet)
+	// 返回顶点遍历序列
+	return res
+}

codes/go/chapter_graph/graph_dfs_test.go

@@ -0,0 +1,28 @@
+// File: graph_dfs_test.go
+// Created Time: 2023-02-18
+// Author: Reanon ([email protected])
+
+package chapter_graph
+
+import (
+	"fmt"
+	"testing"
+
+	. "github.com/krahets/hello-algo/pkg"
+)
+
+func TestGraphDFS(t *testing.T) {
+	/* 初始化无向图 */
+	vets := ValsToVets([]int{0, 1, 2, 3, 4, 5, 6})
+	edges := [][]Vertex{
+		{vets[0], vets[1]}, {vets[0], vets[3]}, {vets[1], vets[2]},
+		{vets[2], vets[5]}, {vets[4], vets[5]}, {vets[5], vets[6]}}
+	graph := newGraphAdjList(edges)
+	fmt.Println("初始化后，图为:")
+	graph.print()
+
+	/* 深度优先遍历 DFS */
+	res := graphDFS(graph, vets[0])
+	fmt.Println("深度优先遍历（DFS）顶点序列为:")
+	PrintSlice(VetsToVals(res))
+}

codes/go/pkg/vertex.go

@@ -0,0 +1,55 @@
+// File: vertex.go
+// Created Time: 2023-02-18
+// Author: Reanon ([email protected])
+
+package pkg
+
+// Vertex 顶点类
+type Vertex struct {
+	Val int
+}
+
+// NewVertex 构造方法
+func NewVertex(val int) Vertex {
+	return Vertex{
+		Val: val,
+	}
+}
+
+// ValsToVets Generate a vertex list tree given an array
+func ValsToVets(vals []int) []Vertex {
+	vets := make([]Vertex, len(vals))
+	for i := 0; i < len(vals); i++ {
+		vets[i] = NewVertex(vals[i])
+	}
+	return vets
+}
+
+// VetsToVals Serialize given vertex list to a value list
+func VetsToVals(vets []Vertex) []int {
+	vals := make([]int, len(vets))
+	for i := range vets {
+		vals[i] = vets[i].Val
+	}
+	return vals
+}
+
+// DeleteSliceElms 删除切片指定元素
+func DeleteSliceElms[T any](a []T, elms ...T) []T {
+	if len(a) == 0 || len(elms) == 0 {
+		return a
+	}
+	// 先将元素转为 set
+	m := make(map[any]struct{})
+	for _, v := range elms {
+		m[v] = struct{}{}
+	}
+	// 过滤掉指定元素
+	res := make([]T, 0, len(a))
+	for _, v := range a {
+		if _, ok := m[v]; !ok {
+			res = append(res, v)
+		}
+	}
+	return res
+}