/**
* The printMark method changes contents of the MazeCell to '#' here invoked Queue is shortest
* path.
*/
public void printMark(MazeCell pathCell) {
pathCell.hash();
while (pathCell.getParent() != null) {
pathCell = pathCell.getParent();
pathCell.hash();
}
}
/**
* BFS routine Using Queue, this solve() method is doing BFS. enqueue all children and dequeue
* them until it gets final point.
*/
public void solve() {
MazeCell N, S, E, W;
Stack<Object> s = new Stack<Object>();
MazeCell startCell = new MazeCell(startx, starty - 1, ' ');
startCell.Mark();
s.push(startCell);
while (!s.isEmpty()) {}
System.out.println();
System.out.println("Maze not solvable!");
System.out.println();
}
/**
* Sorts an ArrayList of MazeCells based on the value of the Heuristic Function
*
* @param neighbors
* @return
*/
private static ArrayList<MazeCell> sortNeighbors(ArrayList<MazeCell> neighbors) {
for (MazeCell temp : neighbors) {
if (temp.getHeuristicDistance() == Integer.MAX_VALUE) {
neighbors.remove(temp);
}
}
// Lowest index has highest path cost
for (int i = 0; i < neighbors.size(); i++) {
for (int j = 1; j < neighbors.size() - i; j++) {
if (neighbors.get(j - 1).getHeuristicDistance() < neighbors.get(j).getHeuristicDistance()) {
MazeCell temp = neighbors.get(j - 1);
neighbors.set(j - 1, neighbors.get(j));
neighbors.set(j, temp);
}
}
}
return neighbors;
}
/** Custom Heuristic Function */
private static int estimatedManhattan(MazeCell currentCell, int goalX, int goalY) {
// Obtain the current path
String currentPath = currentCell.getPath();
// Get the Current Path Cost
int currentPathCost = pathCost(currentPath.toCharArray());
int currNodesExpanded = nodesExpanded;
int length = currentPath.length();
if (length == 0) {
length += 1;
}
// Cost per move
// int averagePathCost = currentPathCost/length;
int averageNodesExpanded = currNodesExpanded / length;
// Get the number of moves left
int distanceLeft = manhattan(goalX, goalY, currentCell.getX(), currentCell.getY());
return averageNodesExpanded * distanceLeft;
}
public void setStart(MazeCell maze_cell) {
this.start = maze_cell;
if (maze_cell.isBlocked()) maze_cell.setCost(1);
}
public void setGoal(MazeCell maze_cell) {
this.goal = maze_cell;
if (maze_cell.isBlocked()) maze_cell.setCost(1);
}
/**
* Implements an A-Star Search on a Maze Object
*
* @param myMaze
* @return
*/
public static char[] aStarSearch(Maze myMaze) {
// For Greedy Best First Search
List<MazeCell> frontier = new LinkedList<MazeCell>();
// Add the Starting State
frontier.add(myMaze.getCell(myMaze.getStartX(), myMaze.getStartY()));
// Store the current Coordinates
int currentX = 0, currentY = 0;
while (!frontier.isEmpty()) {
// Remove the best node based on heuristic path cost and current path cost
int currentNodeIndex = getIndexWithSmallestCurrentPath(frontier);
MazeCell currentNode = frontier.remove(currentNodeIndex);
// Check if this node has been visited
if (currentNode.getVisited() == true) {
continue;
}
// Move the Ghost
// myMaze.scaryGhost.move();
// Mark the current node as visited
currentNode.setVisited();
// Obtain the current coordinates
currentX = currentNode.getX();
currentY = currentNode.getY();
// myMaze.getCell(myMaze.scaryGhost.getGhostX(), myMaze.scaryGhost.getGhostY()).setWall(true);
// The ghost is in the same place
if ((currentX == myMaze.scaryGhost.getGhostX())
&& (currentY == myMaze.scaryGhost.getGhostY())) {
continue;
}
// Reached the Goal State
if ((currentX == myMaze.getGoalX()) && (currentY == myMaze.getGoalY())) {
return myMaze.getCell(myMaze.getGoalX(), myMaze.getGoalY()).getPath().toCharArray();
}
// Increase the number of Expanded Nodes
nodesExpanded += 1;
// Initial values of heuristics
int heuristicRight = Integer.MAX_VALUE,
heuristicLeft = Integer.MAX_VALUE,
heuristicUp = Integer.MAX_VALUE,
heuristicDown = Integer.MAX_VALUE;
// Go Rightwards (0)
if ((!myMaze.getCell(currentX, currentY + 1).isWall())
&& (!myMaze.getCell(currentX, currentY + 1).getVisited())) {
// Obtain the heuristic
// heuristicRight = manhattan(myMaze.getGoalX(), myMaze.getGoalY(), currentX, currentY+1);
heuristicRight =
estimatedManhattan(
myMaze.getCell(currentX, currentY + 1), myMaze.getGoalX(), myMaze.getGoalY());
// Adjust the Path
myMaze
.getCell(currentX, currentY + 1)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "0");
// Set the Heuristic
myMaze.getCell(currentX, currentY + 1).setHeuristicDistance(heuristicRight);
// Find the current path cost
int currentDistanceCost =
pathCost(myMaze.getCell(currentX, currentY + 1).getPath().toCharArray());
// Set the Current Path Distance
myMaze.getCell(currentX, currentY + 1).setCurrentDistanceCost(currentDistanceCost);
}
// Go Downwards (1)
if ((!myMaze.getCell(currentX + 1, currentY).isWall())
&& (!myMaze.getCell(currentX + 1, currentY).getVisited())) {
// Obtain the Heuristic
// heuristicDown = manhattan(myMaze.getGoalX(), myMaze.getGoalY(), currentX+1, currentY);
heuristicDown =
estimatedManhattan(
myMaze.getCell(currentX + 1, currentY), myMaze.getGoalX(), myMaze.getGoalY());
// Adjust the Path
myMaze
.getCell(currentX + 1, currentY)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "1");
// Set the Heuristic
myMaze.getCell(currentX + 1, currentY).setHeuristicDistance(heuristicDown);
// Find the current path cost
int currentDistanceCost =
pathCost(myMaze.getCell(currentX + 1, currentY).getPath().toCharArray());
// Set the Current Path Distance
myMaze.getCell(currentX + 1, currentY).setCurrentDistanceCost(currentDistanceCost);
}
// Go Leftwards (2)
if ((!myMaze.getCell(currentX, currentY - 1).isWall())
&& (!myMaze.getCell(currentX, currentY - 1).getVisited())) {
// Obtain the Heuristic
// heuristicLeft = manhattan(myMaze.getGoalX(), myMaze.getGoalY(), currentX, currentY-1);
heuristicLeft =
estimatedManhattan(
myMaze.getCell(currentX, currentY - 1), myMaze.getGoalX(), myMaze.getGoalY());
// Adjust the Path
myMaze
.getCell(currentX, currentY - 1)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "2");
// Set the Heuristic
myMaze.getCell(currentX, currentY - 1).setHeuristicDistance(heuristicLeft);
// Find the current path cost
int currentDistanceCost =
pathCost(myMaze.getCell(currentX, currentY - 1).getPath().toCharArray());
// Set the Current Path Distance
myMaze.getCell(currentX, currentY - 1).setCurrentDistanceCost(currentDistanceCost);
}
// Go Upwards (3)
if ((!myMaze.getCell(currentX - 1, currentY).isWall())
&& (!myMaze.getCell(currentX - 1, currentY).getVisited())) {
// Obtain the Heuristic
// heuristicUp = manhattan(myMaze.getGoalX(), myMaze.getGoalY(), currentX-1, currentY);
heuristicUp =
estimatedManhattan(
myMaze.getCell(currentX - 1, currentY), myMaze.getGoalX(), myMaze.getGoalY());
// Adjust the Path
myMaze
.getCell(currentX - 1, currentY)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "3");
// Set the Heuristic
myMaze.getCell(currentX - 1, currentY).setHeuristicDistance(heuristicUp);
// Find the current path cost
int currentDistanceCost =
pathCost(myMaze.getCell(currentX - 1, currentY).getPath().toCharArray());
// Set the Current Path Distance
myMaze.getCell(currentX - 1, currentY).setCurrentDistanceCost(currentDistanceCost);
}
// Add the Neighbors to the frontier
if (heuristicRight != Integer.MAX_VALUE) {
frontier.add(myMaze.getCell(currentX, currentY + 1));
}
if (heuristicDown != Integer.MAX_VALUE) {
frontier.add(myMaze.getCell(currentX + 1, currentY));
}
if (heuristicLeft != Integer.MAX_VALUE) {
frontier.add(myMaze.getCell(currentX, currentY - 1));
}
if (heuristicUp != Integer.MAX_VALUE) {
frontier.add(myMaze.getCell(currentX - 1, currentY));
}
// myMaze.getCell(myMaze.scaryGhost.getGhostX(),
// myMaze.scaryGhost.getGhostY()).setWall(false);
}
return myMaze.getCell(myMaze.getGoalX(), myMaze.getGoalY()).getPath().toCharArray();
}
/**
* Implements a Depth First Search on a Maze Object
*
* @param myMaze
* @return
*/
public static char[] depthFirstSearch(Maze myMaze) {
// For breadth-first search
Stack<MazeCell> frontier = new Stack<MazeCell>();
// Add the Starting State
frontier.add(myMaze.getCell(myMaze.getStartX(), myMaze.getStartY()));
while (!frontier.isEmpty()) {
// Get the Top Node
MazeCell currentNode = frontier.pop();
if (currentNode.getVisited() == true) {
continue;
}
// Mark the current node as visited
currentNode.setVisited();
nodesExpanded += 1;
int currentX = currentNode.getX();
int currentY = currentNode.getY();
// Reached the Goal State
if ((currentX == myMaze.getGoalX()) && (currentY == myMaze.getGoalY())) {
return myMaze.getCell(currentX, currentY).getPath().toCharArray();
}
// Go Rightwards (0)
if ((!myMaze.getCell(currentX, currentY + 1).isWall())
&& (!myMaze.getCell(currentX, currentY + 1).getVisited())) {
// Add to the Frontier
frontier.add(myMaze.getCell(currentX, currentY + 1));
// Adjust it's Path
myMaze
.getCell(currentX, currentY + 1)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "0");
}
// Go Downwards (1)
if ((!myMaze.getCell(currentX + 1, currentY).isWall())
&& (!myMaze.getCell(currentX + 1, currentY).getVisited())) {
// Add to the Frontier
frontier.add(myMaze.getCell(currentX + 1, currentY));
// Adjust it's Path
myMaze
.getCell(currentX + 1, currentY)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "1");
}
// Go Leftwards (2)
if ((!myMaze.getCell(currentX, currentY - 1).isWall())
&& (!myMaze.getCell(currentX, currentY - 1).getVisited())) {
// Add to the Frontier
frontier.add(myMaze.getCell(currentX, currentY - 1));
// Adjust it's Path
myMaze
.getCell(currentX, currentY - 1)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "2");
}
// Go Upwards (3)
if ((!myMaze.getCell(currentX - 1, currentY).isWall())
&& (!myMaze.getCell(currentX - 1, currentY).getVisited())) {
// Add to the Frontier
frontier.add(myMaze.getCell(currentX - 1, currentY));
// Adjust it's Path
myMaze
.getCell(currentX - 1, currentY)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "3");
}
}
return null;
}
/**
* Implements a Greedy Best First Search on a Maze Object
*
* @param myMaze
* @return
*/
public static char[] greedyBestFirstSearch(Maze myMaze) {
// For Greedy Best First Search
Stack<MazeCell> frontier = new Stack<MazeCell>();
// Add the Starting State
frontier.add(myMaze.getCell(myMaze.getStartX(), myMaze.getStartY()));
// Store the current Co-ordinates
int currentX = 0, currentY = 0;
while (!frontier.isEmpty()) {
// Get the Top Node
MazeCell currentNode = frontier.pop();
// Check if this node has been visited
if (currentNode.getVisited() == true) {
continue;
}
// Mark the current node as visited
currentNode.setVisited();
// Obtain the current cordinates
currentX = currentNode.getX();
currentY = currentNode.getY();
// Reached the Goal State
if ((currentX == myMaze.getGoalX()) && (currentY == myMaze.getGoalY())) {
return myMaze.getCell(myMaze.getGoalX(), myMaze.getGoalY()).getPath().toCharArray();
}
// Increase the number of Expanded Nodes
nodesExpanded += 1;
// Check that you're not out of Bounds
if (currentX <= 0
|| currentY <= 0
|| currentX >= myMaze.getHeight() - 1
|| currentY >= myMaze.getWidth() - 1) {
continue;
}
// Initial values of heuristics
int heuristicRight = Integer.MAX_VALUE,
heuristicLeft = Integer.MAX_VALUE,
heuristicUp = Integer.MAX_VALUE,
heuristicDown = Integer.MAX_VALUE;
// Go Rightwards (0)
if ((!myMaze.getCell(currentX, currentY + 1).isWall())
&& (!myMaze.getCell(currentX, currentY + 1).getVisited())) {
// Obtain the heuristic
heuristicRight = manhattan(myMaze.getGoalX(), myMaze.getGoalY(), currentX, currentY + 1);
// Adjust the Path
myMaze
.getCell(currentX, currentY + 1)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "0");
// Set the Heuristic
myMaze.getCell(currentX, currentY + 1).setHeuristicDistance(heuristicRight);
}
// Go Downwards (1)
if ((!myMaze.getCell(currentX + 1, currentY).isWall())
&& (!myMaze.getCell(currentX + 1, currentY).getVisited())) {
heuristicDown = manhattan(myMaze.getGoalX(), myMaze.getGoalY(), currentX + 1, currentY);
myMaze
.getCell(currentX + 1, currentY)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "1");
myMaze.getCell(currentX + 1, currentY).setHeuristicDistance(heuristicDown);
}
// Go Leftwards (2)
if ((!myMaze.getCell(currentX, currentY - 1).isWall())
&& (!myMaze.getCell(currentX, currentY - 1).getVisited())) {
heuristicLeft = manhattan(myMaze.getGoalX(), myMaze.getGoalY(), currentX, currentY - 1);
myMaze
.getCell(currentX, currentY - 1)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "2");
myMaze.getCell(currentX, currentY - 1).setHeuristicDistance(heuristicLeft);
}
// Go Upwards (3)
if ((!myMaze.getCell(currentX - 1, currentY).isWall())
&& (!myMaze.getCell(currentX - 1, currentY).getVisited())) {
heuristicUp = manhattan(myMaze.getGoalX(), myMaze.getGoalY(), currentX - 1, currentY);
myMaze
.getCell(currentX - 1, currentY)
.appendPath(myMaze.getCell(currentX, currentY).getPath() + "3");
myMaze.getCell(currentX - 1, currentY).setHeuristicDistance(heuristicUp);
}
// Used to Sort the Values
ArrayList<MazeCell> myNeighbors = new ArrayList<MazeCell>();
if (heuristicRight != Integer.MAX_VALUE) {
myNeighbors.add(myMaze.getCell(currentX, currentY + 1));
}
if (heuristicDown != Integer.MAX_VALUE) {
myNeighbors.add(myMaze.getCell(currentX + 1, currentY));
}
if (heuristicLeft != Integer.MAX_VALUE) {
myNeighbors.add(myMaze.getCell(currentX, currentY - 1));
}
if (heuristicUp != Integer.MAX_VALUE) {
myNeighbors.add(myMaze.getCell(currentX - 1, currentY));
}
// Sort the Cells based on Heuristic Values
myNeighbors = sortNeighbors(myNeighbors);
// Add the Cells to the Frontier in the Sorted Order
for (MazeCell temp : myNeighbors) {
if (temp.getHeuristicDistance() != Integer.MAX_VALUE) {
frontier.add(temp);
}
}
}
return myMaze.getCell(myMaze.getGoalX(), myMaze.getGoalY()).getPath().toCharArray();
}
public void init() {
super.init();
mSet = new TreeSet<KruskalCell>();
mSet.add(this);
}
