node.java

source codes to solve Hexpuzzle problem

import java.util.ArrayList;

public class Node implements Comparable{
		
	// STATE: the state in the state space to which the node corresponds;
	private HexpuzzleItems state;

	// PARENT-NODE: the node in the search tree that generated this node;
	private Node parent;

	// DEPTH: the number of steps along the path from the initial state.
	private int depth;

	Node(HexpuzzleItems state) {
		this.state = state;
		this.depth = 0;
	}

	Node(Node parent, HexpuzzleItems state) {
		this(state);
		this.parent = parent;
		this.depth = parent.getDepth() + 1;
	}
		
	public int getDepth() {
		return depth;
	}

	public int getCost()
	{
		//evaluate the current state's cost
		//f(n) = g(n) + h(n)
		return getDepth() + state.getHeuristicCost();
	}
	
	public boolean goalTest()
	{
		return (this.getState()).goalTest();
	}
	
	public ArrayList<Node> successor()
	{
		ArrayList<Node> nodeList = new ArrayList<Node>();
		
		if(nodeList == null)
			return null;
			
		Item blankItem = state.findBlankItem();		
		if(blankItem != null)
		{			
			ArrayList<Item> itemList = blankItem.getAdjacentItems();
			
			for(int i = 0; i < itemList.size(); i++)
			{
				Item item = itemList.get(i);
				HexpuzzleItems newPuzzleItem = new HexpuzzleItems(state);
				
				if(item != null && newPuzzleItem != null)
				{
					newPuzzleItem.swapItems(item, blankItem);
					
					//create successor Node
					Node newNode = new Node(this, newPuzzleItem);
					nodeList.add(newNode);
				}
			}
		}
		return nodeList;
	}
	
	public boolean isRootNode() {
		return parent == null;
	}

	public Node getParent() {
		return parent;
	}

	public HexpuzzleItems getState() {
		return state;
	}

	public String toString() {
		return getState().toString();
	}

	public int compareTo(Object obj) {
		// TODO Auto-generated method stub
		Node temp = (Node)obj;
		if(this.getCost() == temp.getCost())
		{
			return 0;
		}
		else if(this.getCost() > temp.getCost())
		{
			return 1;
		}
		else
		{
			return -1;
		}
	}
	
	public boolean equals(Object obj)
	{
		Node temp = (Node)obj;
		if(this.getState().equals(temp.getState()))
			return false;
		else
			return true;
	}
}