Created basic Graph (Unweighted ,Undirected )

2026-07-22 18:57:22 -04:00
parent 5f2e548aad
commit b2613bf3e1
2 changed files with 253 additions and 0 deletions
@@ -0,0 +1,84 @@
+package graphs
+
+import "slices"
+
+// undirected, unweighted Graph
+type Graph[T comparable] struct {
+	adjList map[T][]T
+}
+
+// NewGraph() -> Creates an unweighted, undirected graph
+func NewGraph[T comparable]() *Graph[T] {
+	gp := &Graph[T]{
+		adjList: make(map[T][]T),
+	}
+
+	return gp
+}
+
+// AddVertex() -> Creates a new Vertex connecting it to an existing one. Creates them both if
+// they dont exist , if both exist then it adds an edge between them.
+func (gp *Graph[T]) AddVertex(newVertex T, connectToVertex T) {
+	// self loops are not allowed in this graph
+	if newVertex == connectToVertex {
+		return
+	}
+
+	if !slices.Contains(gp.adjList[newVertex], connectToVertex) {
+		gp.adjList[newVertex] = append(gp.adjList[newVertex], connectToVertex)
+	}
+
+	if !slices.Contains(gp.adjList[connectToVertex], newVertex) {
+		gp.adjList[connectToVertex] = append(gp.adjList[connectToVertex], newVertex)
+	}
+}
+
+// AddIsolatedVertex() -> Creates an isolated Vertex returns True if ok ,
+// false if vertex already exist
+func (gp *Graph[T]) AddIsolatedVertex(newVertex T) bool {
+	_, ok := gp.adjList[newVertex]
+	if !ok {
+		gp.adjList[newVertex] = make([]T, 0)
+		return true
+	}
+	return false
+}
+
+// ConnectEdges() -> Connects an existing vertex to several vertices
+func (gp *Graph[T]) ConnectEdges(vertex T, uwu ...T) bool {
+	_, ok := gp.adjList[vertex]
+
+	for _, edge := range uwu {
+
+		_, ok = gp.adjList[edge]
+		if !ok {
+			return ok
+		}
+	}
+
+	for _, edge := range uwu {
+		gp.AddVertex(vertex, edge)
+	}
+
+	return ok
+}
+
+// Order() -> returns the amount of Vertices
+func (gp *Graph[T]) Order() int {
+	return len(gp.adjList)
+}
+
+// Size() -> returns the amount of Edges
+func (gp *Graph[T]) Size() int {
+	var size int
+
+	for _, val := range gp.adjList {
+		size += len(val)
+	}
+	return size / 2
+}
+
+// Display() -> returns adjList[map]T []T
+func (gp *Graph[T]) Display() map[T][]T {
+	return gp.adjList
+}
@@ -0,0 +1,169 @@
+package tests
+
+import (
+	"slices"
+	"testing"
+
+	"datastructures/graphs"
+)
+
+func TestNewGraphIsEmpty(t *testing.T) {
+	graph := graphs.NewGraph[int]()
+
+	if graph.Order() != 0 {
+		t.Errorf("new graph Order = %d, want 0", graph.Order())
+	}
+	if graph.Size() != 0 {
+		t.Errorf("new graph Size = %d, want 0", graph.Size())
+	}
+}
+
+func TestAddVertexCreatesBothAndConnects(t *testing.T) {
+	graph := graphs.NewGraph[string]()
+	graph.AddVertex("a", "b")
+
+	if graph.Order() != 2 {
+		t.Errorf("Order = %d, want 2", graph.Order())
+	}
+	if graph.Size() != 1 {
+		t.Errorf("Size = %d, want 1", graph.Size())
+	}
+
+	adjacency := graph.Display()
+	if !slices.Contains(adjacency["a"], "b") {
+		t.Errorf("expected b in a's adjacency, got %v", adjacency["a"])
+	}
+	if !slices.Contains(adjacency["b"], "a") {
+		t.Errorf("expected a in b's adjacency (undirected), got %v", adjacency["b"])
+	}
+}
+
+func TestAddVertexIsIdempotentForEdges(t *testing.T) {
+	graph := graphs.NewGraph[string]()
+	graph.AddVertex("a", "b")
+	graph.AddVertex("a", "b")
+	graph.AddVertex("b", "a")
+
+	adjacency := graph.Display()
+	if len(adjacency["a"]) != 1 {
+		t.Errorf("expected no duplicate edges in a, got %v", adjacency["a"])
+	}
+	if len(adjacency["b"]) != 1 {
+		t.Errorf("expected no duplicate edges in b, got %v", adjacency["b"])
+	}
+	if graph.Size() != 1 {
+		t.Errorf("Size = %d, want 1", graph.Size())
+	}
+}
+
+func TestAddVertexMultipleEdges(t *testing.T) {
+	graph := graphs.NewGraph[int]()
+	graph.AddVertex(1, 2)
+	graph.AddVertex(1, 3)
+	graph.AddVertex(1, 4)
+
+	if graph.Order() != 4 {
+		t.Errorf("Order = %d, want 4", graph.Order())
+	}
+	if graph.Size() != 3 {
+		t.Errorf("Size = %d, want 3", graph.Size())
+	}
+	if len(graph.Display()[1]) != 3 {
+		t.Errorf("expected vertex 1 to have degree 3, got %v", graph.Display()[1])
+	}
+}
+
+func TestAddIsolatedVertex(t *testing.T) {
+	graph := graphs.NewGraph[string]()
+
+	if !graph.AddIsolatedVertex("solo") {
+		t.Error("AddIsolatedVertex on new vertex = false, want true")
+	}
+	if graph.AddIsolatedVertex("solo") {
+		t.Error("AddIsolatedVertex on existing vertex = true, want false")
+	}
+
+	if graph.Order() != 1 {
+		t.Errorf("Order = %d, want 1", graph.Order())
+	}
+	if graph.Size() != 0 {
+		t.Errorf("isolated vertex should add no edges, Size = %d", graph.Size())
+	}
+	if len(graph.Display()["solo"]) != 0 {
+		t.Errorf("isolated vertex should have empty adjacency, got %v", graph.Display()["solo"])
+	}
+}
+
+func TestConnectEdgesAllExisting(t *testing.T) {
+	graph := graphs.NewGraph[int]()
+	graph.AddIsolatedVertex(1)
+	graph.AddIsolatedVertex(2)
+	graph.AddIsolatedVertex(3)
+	graph.AddIsolatedVertex(4)
+
+	if !graph.ConnectEdges(1, 2, 3, 4) {
+		t.Error("ConnectEdges with all existing vertices = false, want true")
+	}
+	if graph.Size() != 3 {
+		t.Errorf("Size = %d, want 3", graph.Size())
+	}
+	if len(graph.Display()[1]) != 3 {
+		t.Errorf("expected vertex 1 to connect to 3 vertices, got %v", graph.Display()[1])
+	}
+	// undirected: each target should point back at 1
+	for _, target := range []int{2, 3, 4} {
+		if !slices.Contains(graph.Display()[target], 1) {
+			t.Errorf("expected vertex %d to point back at 1, got %v", target, graph.Display()[target])
+		}
+	}
+}
+
+func TestConnectEdgesRejectsMissingVertex(t *testing.T) {
+	graph := graphs.NewGraph[int]()
+	graph.AddIsolatedVertex(1)
+	graph.AddIsolatedVertex(2)
+	// 99 does not exist
+
+	if graph.ConnectEdges(1, 2, 99) {
+		t.Error("ConnectEdges with a missing target = true, want false")
+	}
+	// nothing should have been connected (atomic)
+	if graph.Size() != 0 {
+		t.Errorf("no edges should be added on failure, Size = %d", graph.Size())
+	}
+	if len(graph.Display()[1]) != 0 {
+		t.Errorf("vertex 1 should remain isolated on failure, got %v", graph.Display()[1])
+	}
+}
+
+func TestSelfLoopIsRejected(t *testing.T) {
+	graph := graphs.NewGraph[int]()
+	graph.AddVertex(1, 1)
+
+	if graph.Size() != 0 {
+		t.Errorf("self-loop should add no edge, Size = %d", graph.Size())
+	}
+	if slices.Contains(graph.Display()[1], 1) {
+		t.Errorf("vertex 1 should not contain itself, got %v", graph.Display()[1])
+	}
+
+	// a real edge on the same vertex must still work
+	graph.AddVertex(1, 2)
+	if graph.Size() != 1 {
+		t.Errorf("Size = %d, want 1 after a valid edge", graph.Size())
+	}
+}
+
+func TestOrderAndSize(t *testing.T) {
+	graph := graphs.NewGraph[string]()
+	graph.AddVertex("a", "b")
+	graph.AddVertex("b", "c")
+	graph.AddVertex("c", "a")
+
+	if graph.Order() != 3 {
+		t.Errorf("Order = %d, want 3 (triangle)", graph.Order())
+	}
+	if graph.Size() != 3 {
+		t.Errorf("Size = %d, want 3 (triangle)", graph.Size())
+	}
+}