Question

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
    }
}

Answer 1

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.