Graph: Implementation in java

What is a Graph?

Application of Graph

-- Graph is a nonlinear data structure.

-- Edge and Vertex are the main components of the graph.

Type

-- Directed Graph: If an edge implies one direction then it called Directed Graph.

-- Undirected Graph: If the connection between vertices is symmetric means A connected with B ⇔ B connected with A.

Path

we can reach India to Germany via the UK because from the above image we can't directly reach Germany.
so (INDIA -> UK -> GERMANY) is one path of the other paths.
Here, INDIA, UK and others are the nodes(vertices).
This graph is directed.

One node can be connected with one node or two nodes or all nodes also in the graph.

Generate a Directed Graph (Code In Java)

class Graph {
int v; // total vertex of Graph
LinkedList<Integer> edge[];

// Constructor will assign the value of v and will
//create the v number of LinkedList
public Graph(int v) {
this.v = v;
edge = new LinkedList[v];
for (int i = 0; i < this.v; i++) {
edge[i] = new LinkedList<Integer>();
}
}

// This method is used to connecting one node to another node
// It takes three parameters
//first is graph object
//source node
//destination node
public void connectVertex(Graph g, int source, int dest) {
g.edge[source - 1].add(dest - 1);
}

//This method will print the final graph
public void showGraph(Graph g) {
for (int i = 0; i < this.v; i++) {
System.out.print(i+1);
for (int j : g.edge[i])
System.out.print("->" + (j + 1));
System.out.println();
}
}

}

edge is an array of LinkedList because we have to remember which node is connected with which edge.

we can define an array of LinkedList

LinkedList<E> name = new LinkedList[size_of_array]

Remain code is

public class GenerateGraph {

public static void main(String[] args) {
Graph g = new Graph(5); // This Graph have 5 nodes

g.connectVertex(g, 1, 2);
g.connectVertex(g, 2, 1);
g.connectVertex(g, 2, 3);
g.connectVertex(g, 3, 4);
g.connectVertex(g, 4, 5);
g.connectVertex(g, 5, 1);

g.showGraph(g);
}

}