EightPuzzle.java

public class EightPuzzle {	
	public static void main(String[] args) {
		int eCount = 0, tempNum, ans = 0, num = 0;				// Reply the user enters and the num is the counter for the frontier
		int[][] temp = new int[3][3], goal = { {0,1,2}, {3,4,5}, {6,7,8} };
		boolean play = true, h_1 = true, finished = false;
		Scanner kb = new Scanner(System.in);
		Node[] frontier = new Node[200], path;
		Node[][] explored = new Node[55][80];	// Holds all previous states that are not in the frontier by their cost
		Node root = new Node(), copy, min;			// Copy save the root for the second heuristic	
		
		for(int h = 0; h < 55; h++) {
			for(int g = 0; g < 80; g++) {
				explored[h][g] = new Node();
			}
		}
		
public static int checkFrontier(Node[] f, Node[][] e, int num) {
		// The purpose of this method is to see if any of the states that are in the frontier 
		// have already been expanded. This method sifts through the expanded hash table using the
		// cost of the state as the index. If a state has already been visited it will be deleted
		// from the frontier and num will be reduced by one.
		int temp = num;	// If num needs to be reduced temp will keep track of it
		int count = 0;	// Indexes through the 2nd dimension of the hash table
		boolean repeat = true, runWhile = true;
		
		//System.out.println("The number of states in the frontier is: " + num);
		
		for(int i = 0; i < num; i++) {		// Runs through all states in the frontier
			int pra = f[i].getCost();
			Node[] tlo = e[pra];
			System.out.println("First index = " + pra);
			System.out.println("i = " + i);
			System.out.println("num = " + num);
			checkIfEmpty(e[f[i].getCost()][count].puzzle);
			while(!checkIfEmpty(e[f[i].getCost()][count].puzzle) && runWhile) {	// While the explored list is not null for the specified index
				System.out.println("Count = " + count);
				for(int j = 0; j < 3; j++) {							// Runs through the state's puzzle in frontier and explored
					for(int k = 0; k < 3; k++) {						// and compares the two
							if(f[i].puzzle[j][k] != e[f[i].getCost()][count].puzzle[j][k])	// If one term from the puzzles does not match
								repeat = false;												// the states are not equal to one another
					}
				}
				if(count + 1 < 80)
					count++;
				else
					runWhile = false;
				if(repeat) {			// If the states are equal	
					temp--;		
					f[i] = null;		// Remove the state from the frontier
					runWhile = false;	// Stop looking at the explored list with this state
				}
				try {
					checkIfEmpty(e[f[i].getCost()][count].puzzle);
				} catch(NullPointerException ex) {
					runWhile = false;
				}
			}
			repeat = true;
			count = 0;
		}
		
		if(num != temp) {		// If a state was deleted then shift over the frontier
			for(int l = 0; l < num; l++) {
				if(f[l] == null) {
					f[l] = f[l + 1];
					f[l + 1] = null;
				}
			}
			num = temp;		// Adjust num
		}
		return num;
	}