bfs

Author: xiaomeng79

algorithms/graphs/README.md

@@ -4,6 +4,16 @@
 
 #### 深度优先DFS(Depth First Search)
 
+如: 树的先序遍历 
+
 思想:假设所有顶点均未被访问，从一个顶点V出发，依次访问它的各个邻接点，直到图中所有和V相通的点都被访问到，若还有未访问的顶点，重复以上过程
 
+栈
+
 #### 广度优先BFS(Breadth First Search)
+
+如：树的层次遍历
+
+思想: 从顶点V出发，访问V之后依次访问v的各个未曾访问过的邻接点，然后分别从这些邻接点出发依次访问它们的邻接点
+
+队列

algorithms/graphs/bfs/bfs.go

@@ -1 +1,27 @@
 package bfs
+
+import "github.com/xiaomeng79/go-algorithm/data-structures/graph"
+
+//有向图的广度优先搜索
+func Bfs(g *graph.DirGraph, start graph.VertexId, fn func(graph.VertexId)) {
+	queue := []graph.VertexId{start}
+	visited := make(map[graph.VertexId]bool)
+
+	var next []graph.VertexId
+
+	for len(queue) > 0 {
+		next = []graph.VertexId{}
+		for _, vertex := range queue {
+			visited[vertex] = true
+			//获取邻接点
+			neighbours := g.GetNeighbours(vertex).VerticesIter()
+			fn(vertex)
+			for neighbour := range neighbours {
+				if _, ok := visited[neighbour]; !ok {
+					next = append(next, neighbour)
+				}
+			}
+		}
+		queue = next
+	}
+}

algorithms/graphs/bfs/bfs_test.go

@@ -1 +1,24 @@
 package bfs
+
+import (
+	"github.com/stretchr/testify/assert"
+	"github.com/xiaomeng79/go-algorithm/data-structures/graph"
+	"testing"
+)
+
+func TestBfs(t *testing.T) {
+	h := graph.NewDirected()
+
+	for i := 0; i < 10; i++ {
+		h.AddVertex(graph.VertexId(i))
+	}
+
+	for i := 0; i < 9; i++ {
+		h.AddEdge(graph.VertexId(i), graph.VertexId(i+1), 1)
+	}
+	count := 0
+	Bfs(h, graph.VertexId(3), func(id graph.VertexId) {
+		count += int(id)
+	})
+	assert.Equal(t, 42, count)
+}

algorithms/graphs/dfs/dfs_test.go

@@ -11,18 +11,18 @@ func TestUndirectedDfs(t *testing.T) {
 	h := graph.NewUndirected()
 
 	//增加顶点，
-	for i:=0; i<10; i++ {
+	for i := 0; i < 10; i++ {
 		h.AddVertex(graph.VertexId(i))
 	}
 	//增加边
-	for i:=0;i<9;i++ {
-		h.AddEdge(graph.VertexId(i),graph.VertexId(i+1),1)
+	for i := 0; i < 9; i++ {
+		h.AddEdge(graph.VertexId(i), graph.VertexId(i+1), 1)
 	}
 	counter := 0
-	UndirectedDfs(h,graph.VertexId(4), func(id graph.VertexId) {
+	UndirectedDfs(h, graph.VertexId(4), func(id graph.VertexId) {
 		counter += int(id)
 	})
-	assert.Equal(t,45,counter)
+	assert.Equal(t, 45, counter)
 }
 
 func TestDirectedDfs(t *testing.T) {
@@ -43,5 +43,5 @@ func TestDirectedDfs(t *testing.T) {
 		counter += int(v)
 	})
 
-	assert.Equal(t,42,counter)
-}
+	assert.Equal(t, 42, counter)
+}