add digraph

Author: shellfly

cmd/digraph/main.go

@@ -0,0 +1,41 @@
+/*
+   Execution:    go run cmd/digraph/main.go input.txt
+   Dependencies: Bag.java Stack.java In.java StdOut.java
+   Data files:   https://algs4.cs.princeton.edu/41graph/tinyDG.txt
+                 https://algs4.cs.princeton.edu/41graph/mediumDG.txt
+                 https://algs4.cs.princeton.edu/41graph/largeDG.txt
+
+   A graph, implemented using an array of sets.
+   Parallel edges and self-loops are permitted.
+
+   % go run cmd/digraph/main.go < tinyDG.txt
+   13 vertices, 22 edges
+   0: 5 1
+   1:
+   2: 0 3
+   3: 5 2
+   4: 3 2
+   5: 4
+   6: 9 4 8 0
+   7: 6 9
+   8: 6
+   9: 11 10
+   10: 12
+   11: 4 12
+   12: 9
+*/
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/shellfly/algo"
+	"github.com/shellfly/algo/stdin"
+)
+
+func main() {
+	graph := algo.NewDigraph(stdin.NewIn(os.Args[1]))
+	fmt.Println(graph)
+}

digraph.go

@@ -0,0 +1,86 @@
+package algo
+
+import (
+	"fmt"
+
+	"github.com/shellfly/algo/stdin"
+)
+
+// Digraph ...
+type Digraph struct {
+	v, e int
+	adj  []*Bag
+}
+
+// NewDigraph ...
+func NewDigraph(in *stdin.In) *Digraph {
+	v := in.ReadInt()
+	adj := make([]*Bag, v)
+	for i := 0; i < v; i++ {
+		adj[i] = NewBag()
+	}
+	g := &Digraph{v: v, e: 0, adj: adj}
+	e := in.ReadInt()
+	for i := 0; i < e; i++ {
+		v, w := in.ReadInt(), in.ReadInt()
+		g.AddEdge(v, w)
+	}
+	return g
+}
+
+// NewDigraphV ...
+func NewDigraphV(v int) *Digraph {
+	adj := make([]*Bag, v)
+	for i := 0; i < v; i++ {
+		adj[i] = NewBag()
+	}
+	return &Digraph{v: v, e: 0, adj: adj}
+}
+
+// V ...
+func (g *Digraph) V() int {
+	return g.v
+}
+
+// E ...
+func (g *Digraph) E() int {
+	return g.e
+}
+
+// AddEdge ...
+func (g *Digraph) AddEdge(v, w int) {
+	g.adj[v].Add(w)
+	g.e++
+}
+
+// Adj ...
+func (g *Digraph) Adj(v int) []int {
+	var items []int
+	for _, item := range g.adj[v].Slice() {
+		items = append(items, item.(int))
+	}
+	return items
+}
+
+// Reverse ...
+func (g *Digraph) Reverse() *Digraph {
+	r := NewDigraphV(g.v)
+	for v := 0; v < g.v; v++ {
+		for _, w := range g.Adj(v) {
+			r.AddEdge(w, w)
+		}
+	}
+	return r
+}
+
+func (g *Digraph) String() string {
+	s := fmt.Sprintf("%d vertices, %d edges\n", g.v, g.e)
+	for i := 0; i < g.v; i++ {
+		var adjs string
+		for _, w := range g.Adj(i) {
+			adjs = adjs + fmt.Sprintf(" %d", w)
+		}
+		s += fmt.Sprintf("%d: %s\n", i, adjs)
+	}
+	return s
+}