//Here's a simple graph data structure

package main

​

import "fmt"

​

//Here is the structure for the graph containg the vertex

type Graph struct {

    vertices []*Vertex

}

​

//The vertex are the key data point

type Vertex struct {

    key int

    ajecent []*Vertex

}

​

//This function adds a vertex to the graph

func (g *Graph) AddVertex(k int) {

    //The error avoids duplicate vertex

    if contains(g.vertices, k) {

        err := fmt.Errorf("cannot add because vertex %v's already exist", k)

        fmt.Println(err.Error())

    }else {

    //This appends an vertex

    g.vertices = append(g.vertices, &Vertex{key: k})    

    }

}

//This function adds an edge to the graph

func (g *Graph) AddEdge(from, to int) {

    //Variables for where the edges are

    fromVertex := g.GetVertex(from)

    toVertex := g.GetVertex(to)

    if fromVertex == nil || toVertex == nil {

        //Tis error avoids creating edges that don't exist

        err := fmt.Errorf("(%v ---> %v) is an invalid edge", from, to)

        fmt.Println(err.Error())

    }else if contains(fromVertex.ajecent, to){

                //Tis error avoids creating edges that already exist

        err := fmt.Errorf("(%v ---> %v) edge already exist", from, to)

        fmt.Println(err.Error())

    }else {

        //Add edge

        fromVertex.ajecent = append(fromVertex.ajecent, toVertex)

    }

}

​

//Get the vertex

func (g *Graph) GetVertex(k int) *Vertex {

    for i, v := range g.vertices {

        if v.key ==k {

            return g.vertices[i]

        }

    }

    return nil

}

​

//contains

func contains(s []*Vertex,k int) bool {

    for _, v := range s {

        if k == v.key {

            return true

        }

    }

    return false

}

​

//This print's the vertex

func (g *Graph) Print()  {

    for _, v := range g.vertices {

        fmt.Printf("\nVertex %v:", v.key)

        for _, v := range v.ajecent {

            fmt.Printf(" %v ", v.key)           

        }

    }

    fmt.Println()

}

​

func main() {

    myGraph := &Graph{}//Creating a new graph

    for i := 0; i < 10; i++ {//Creating 10 vertices

        myGraph.AddVertex(i)

    }

​

    myGraph.AddVertex(10)//Add a vertex

    myGraph.AddEdge(5,7)//Add an edge

    myGraph.AddEdge(15,5)//Add an invalid edge

    myGraph.AddEdge(7,5)//Add a edge

    myGraph.AddEdge(7,5)//Add a duplicate edge 

​

    myGraph.Print()

}