CODEWITHSUNDEEP
javaalgorithm
Dragon
Dragon

Reputation: 2481

How to make backward node connection in a graph?

I have a graph with 4 nodes which are connected with other nodes. Each connection has weight. For example:

A -> 5 -> B

A -> 3 -> C

B -> 4 -> C

B -> 3 -> D

Each node has backward connection correspondingly. But I have a problem with realization of such backward connection. Here is algorithm (in words) of what I have now:

  1. Create nodes (A, B, C, D)
  2. Connect node A to node B
  3. Set connection weight
  4. Repeat 2,3 for other nodes.

Following this algorithm I have to make backward connections (node B to node A) separately. And if I have 100 nodes or more, it'll be a trial for my attention.

How to make these backward connections during connection creation?

Here is a Node class:

public class Node {
    private String name;
    private Map<Node, Integer> connections;

    public Node(String name) {
        this.name = name;
        connections = new HashMap<Node, Integer>();
    }

    public void connect(Node node, int weight) {
        connections.put(node, weight);
        //It is expected to make backward connection here
    }
}

Upvotes: 2

Views: 204

Answers (2)

Azodious
Azodious

Reputation: 13872

You can use:

node.getConnections().put(this, weight);

But, i'll recommend a design change:

class Node
{
    String name;
    List<Node> connectedNodes;
}

class Branch
{
    Node a; 
    Node b;
    int weight;
}

// calling part of program
// initizaliztion of fields already done
public void connect(Node node1, Node node2, int weight) 
{
    // checks required:
    // if a branch already exists

    node1.connectedNodes.Add(node2);
    node2.connectedNodes.Add(node1);

    Branch branch = new Branch(node1, node2, weight);
}

Upvotes: 2

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726599

Like this:

public void connect(Node node, int weight) {
    connections.put(node, weight);
    node.connections.put(this, weight);
}

Since Node is used as the key in the connections map, don't forget to override its equals and hashCode methods.

Upvotes: 3

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