// Method to run the overall A* algorithm and print the results to console
public static void Run()
{
// Create the open and closed lists
var frontier = new MinHeap <BoardNode>();
var visited = new List <BoardState>();
// Variables to show the amount of nodes generated and the cost
int numExpanded = 0;
int numGenerated = 0;
int pathCost = 0;
// Create node to interate through open list
BoardNode current = null;
// Create Node for the starting state
BoardNode initialState;
// Ask for user starting and goal states until configuration is possible
do
{
// Ask user for goal state
goalState = getGoal();
// Ask user for starting state
initialState = getInitial();
}while (!goalState.checkPolarity(initialState.State));
// Print starting and goal nodes
Logger.WriteLine("Initial State: ");
initialState.State.PrintBoard();
Logger.WriteLine("Goal State: ");
goalState.PrintBoard();
// Add starting state to the open list
frontier.Add(initialState);
// While the open list is not empty
while (!frontier.IsEmpty())
{
// Store the best move from the open list
current = frontier.RemoveMin();
numExpanded++;
// If the current node is the goal
if (current.GoalNode)
{
// Set the path cost and break from the loop
pathCost = current.GVal;
break;
}
// Add the current state to the closed list
visited.Add(current.State);
// Retrieve the nodes around the current node
var successors = current.GenerateSuccessors().Where(successor => !visited.Contains(successor.State));
numGenerated += successors.ToList().Count;
// Add each successor to the open list
foreach (var successor in successors)
{
frontier.Add(successor);
}
}
// Create a stack to store the path
var path = new Stack <BoardNode>();
// Starting from the goal, push each parent to the stack
while (current != null)
{
path.Push(current);
current = current.Parent;
}
Logger.WriteLine("Path found. Showing path... ");
Logger.WriteLine();
// For each node in the path
foreach (var item in path)
{
// Print the board
item.State.PrintBoard();
// If the user chose the misplaced tile heuristic
if (initialState.UseMisplacedHeuristic)
{
// Print the misplaced tile heuristic
Logger.WriteLine($"Misplaced Heuristic: {item.HValMisplaced}");
}
else
{
// Print the manhattan distance heuristic
Logger.WriteLine($"Manhattan Heuristic: {item.HValManhat}");
}
// Print the G and F values
Logger.WriteLine($"G Value: {item.GVal}");
Logger.WriteLine($"F Value: {item.FVal}");
Logger.WriteLine();
}
// Print the number of nodes generated, expanded, and the path cost
Logger.WriteLine("Number of Nodes Generated: " + numGenerated);
Logger.WriteLine("Number of Nodes Expanded: " + numExpanded);
Logger.WriteLine("Total Path Cost: " + pathCost);
}
// Method to allow user input of the starting state and heuristic
private static BoardNode getInitial()
{
// Create variables to get user input for starting state
BoardNode init;
string[] start;
char input1;
char input2;
// While the input is invalid
do
{
// Ask user if they would like to create a custom starting state
Console.WriteLine("Would you like to create an intial state? (Y/N) ");
input1 = Console.ReadLine().ToCharArray()[0];
Console.WriteLine();
}while (char.ToUpper(input1) != 'Y' && char.ToUpper(input1) != 'N');
// If the user wants to create an initial state
if (char.ToUpper(input1) == 'Y')
{
// While the input is invalid
do
{
// Ask user to input starting state
Console.WriteLine("Please enter the starting state(1, 2, ... 8, 0): ");
start = Regex.Split(Console.ReadLine(), @"\D+");
Console.WriteLine();
}while (BoardState.SetBoard(start) == null);
// While the input is invalid
do
{
// Ask user if they would like to use the misplaced tile heuristic
Console.WriteLine("Would you like to use the Misplaced Tile Heuristic? (Y/N) ");
input2 = Console.ReadLine().ToCharArray()[0];
Console.WriteLine();
}while (char.ToUpper(input2) != 'Y' && char.ToUpper(input2) != 'N');
// If the user wants to use the misplaced tile heuristic
if (char.ToUpper(input2) == 'Y')
{
// Create node with the custom starting board and misplaced tile heuristic
init = new BoardNode(BoardState.SetBoard(start), 0, true, null);
}
else
{
// Create node with the custom starting board and the manhattan distance heuristic
init = new BoardNode(BoardState.SetBoard(start), 0, false, null);
}
}
else
{
// While the input is invalid
do
{
// Ask the user if they would like to use the misplaced tile heuristic
Console.WriteLine("Would you like to use the Misplaced Tile Heuristic? (Y/N) ");
input2 = Console.ReadLine().ToCharArray()[0];
Console.WriteLine();
}while (char.ToUpper(input2) != 'Y' && char.ToUpper(input2) != 'N');
// If the user wants to use the misplaced tile heuristic
if (char.ToUpper(input2) == 'Y')
{
// Create node using random board and misplaced tile heuristic
init = new BoardNode(BoardState.BuildRandomBoard(), 0, true, null);
}
else
{
// Create node using random board and manhattan distance heuristic
init = new BoardNode(BoardState.BuildRandomBoard(), 0, false, null);
}
}
// Return the created node as the starting node
return(init);
}