How to resolve the algorithm Sokoban step by step in the C# programming language
How to resolve the algorithm Sokoban step by step in the C# programming language
Table of Contents
Problem Statement
Demonstrate how to find a solution to a given Sokoban level. For the purpose of this task (formally, a PSPACE-complete problem) any method may be used. However a move-optimal or push-optimal (or any other -optimal) solutions is preferred. Sokoban levels are usually stored as a character array where Sokoban solutions are usually stored in the LURD format, where lowercase l, u, r and d represent a move in that (left, up, right, down) direction and capital LURD represents a push. Please state if you use some other format for either the input or output, and why. For more information, see the Sokoban wiki.
Let's start with the solution:
Step by Step solution about How to resolve the algorithm Sokoban step by step in the C# programming language
The provided C# code is a solver for the classic Sokoban puzzle game. It takes a level description as input and returns a solution sequence of moves if one exists. Here's a detailed explanation of the code:
-
Class Structure: The code defines two nested classes:
Board: Represents the game board. It contains the current game board state (Cur), the solution sequence (Sol), and the player's current position (XandY).SokobanSolver: The main class that implements the puzzle solver.
-
Constructor (
SokobanSolvermethod): Initializes the solver with the given game board description. It iterates through the board to build thedestBoard(destination board with only boxes and empty spaces) andcurrBoard(current board with all non-empty cells). It also tracks the initial player position. -
Movemethod: Simulates moving the player from the current position in the specified direction (dxanddy) if the destination cell is empty. It returns the new game board state after the move ornullif the move is not possible. -
Pushmethod: Simulates pushing a box from the current position in the specified direction (dxanddy) if both the destination cell and the cell behind it are empty. It returns the new game board state after the push ornullif the push is not possible. -
IsSolvedmethod: Checks if the given game board state meets the winning condition, where all boxes are in their designated target positions. -
Solvemethod: Implements the main puzzle-solving algorithm. It uses a Breadth-First Search approach with the following steps:- Initializes data structures for tracking visited boards (
history) and a queue of board states to explore (open). - Adds the initial board state to both
historyandopen. - Iterates through possible moves and pushes from the player's current position, checking if they lead to a solution or have already been explored (
history). - If a solution is found, it returns the sequence of moves that lead to it. Otherwise, it continues exploring until no more moves can be made, and returns "No solution" if no solution is found.
- Initializes data structures for tracking visited boards (
-
Mainmethod: Acts as the entry point for the program. It initializes a test game board, prints the initial board state, and invokes theSolvemethod to find and print the solution sequence or "No solution" if no solution exists.
In summary, this code provides a Sokoban puzzle solver that uses a Breadth-First Search algorithm to explore possible moves and pushes, efficiently finding a solution sequence if one exists.
Source code in the csharp programming language
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace SokobanSolver
{
public class SokobanSolver
{
private class Board
{
public string Cur { get; internal set; }
public string Sol { get; internal set; }
public int X { get; internal set; }
public int Y { get; internal set; }
public Board(string cur, string sol, int x, int y)
{
Cur = cur;
Sol = sol;
X = x;
Y = y;
}
}
private string destBoard, currBoard;
private int playerX, playerY, nCols;
SokobanSolver(string[] board)
{
nCols = board[0].Length;
StringBuilder destBuf = new StringBuilder();
StringBuilder currBuf = new StringBuilder();
for (int r = 0; r < board.Length; r++)
{
for (int c = 0; c < nCols; c++)
{
char ch = board[r][c];
destBuf.Append(ch != '$' && ch != '@' ? ch : ' ');
currBuf.Append(ch != '.' ? ch : ' ');
if (ch == '@')
{
this.playerX = c;
this.playerY = r;
}
}
}
destBoard = destBuf.ToString();
currBoard = currBuf.ToString();
}
private string Move(int x, int y, int dx, int dy, string trialBoard)
{
int newPlayerPos = (y + dy) * nCols + x + dx;
if (trialBoard[newPlayerPos] != ' ')
return null;
char[] trial = trialBoard.ToCharArray();
trial[y * nCols + x] = ' ';
trial[newPlayerPos] = '@';
return new string(trial);
}
private string Push(int x, int y, int dx, int dy, string trialBoard)
{
int newBoxPos = (y + 2 * dy) * nCols + x + 2 * dx;
if (trialBoard[newBoxPos] != ' ')
return null;
char[] trial = trialBoard.ToCharArray();
trial[y * nCols + x] = ' ';
trial[(y + dy) * nCols + x + dx] = '@';
trial[newBoxPos] = '$';
return new string(trial);
}
private bool IsSolved(string trialBoard)
{
for (int i = 0; i < trialBoard.Length; i++)
if ((destBoard[i] == '.')
!= (trialBoard[i] == '$'))
return false;
return true;
}
private string Solve()
{
char[,] dirLabels = { { 'u', 'U' }, { 'r', 'R' }, { 'd', 'D' }, { 'l', 'L' } };
int[,] dirs = { { 0, -1 }, { 1, 0 }, { 0, 1 }, { -1, 0 } };
ISet<string> history = new HashSet<string>();
LinkedList<Board> open = new LinkedList<Board>();
history.Add(currBoard);
open.AddLast(new Board(currBoard, string.Empty, playerX, playerY));
while (!open.Count.Equals(0))
{
Board item = open.First();
open.RemoveFirst();
string cur = item.Cur;
string sol = item.Sol;
int x = item.X;
int y = item.Y;
for (int i = 0; i < dirs.GetLength(0); i++)
{
string trial = cur;
int dx = dirs[i, 0];
int dy = dirs[i, 1];
// are we standing next to a box ?
if (trial[(y + dy) * nCols + x + dx] == '$')
{
// can we push it ?
if ((trial = Push(x, y, dx, dy, trial)) != null)
{
// or did we already try this one ?
if (!history.Contains(trial))
{
string newSol = sol + dirLabels[i, 1];
if (IsSolved(trial))
return newSol;
open.AddLast(new Board(trial, newSol, x + dx, y + dy));
history.Add(trial);
}
}
// otherwise try changing position
}
else if ((trial = Move(x, y, dx, dy, trial)) != null)
{
if (!history.Contains(trial))
{
string newSol = sol + dirLabels[i, 0];
open.AddLast(new Board(trial, newSol, x + dx, y + dy));
history.Add(trial);
}
}
}
}
return "No solution";
}
public static void Main(string[] a)
{
string level = "#######," +
"# #," +
"# #," +
"#. # #," +
"#. $$ #," +
"#.$$ #," +
"#.# @#," +
"#######";
System.Console.WriteLine("Level:\n");
foreach (string line in level.Split(','))
{
System.Console.WriteLine(line);
}
System.Console.WriteLine("\nSolution:\n");
System.Console.WriteLine(new SokobanSolver(level.Split(',')).Solve());
}
}
}
You may also check:How to resolve the algorithm Hilbert curve step by step in the Ruby programming language
You may also check:How to resolve the algorithm Convert seconds to compound duration step by step in the Quackery programming language
You may also check:How to resolve the algorithm Loops/Nested step by step in the SPL programming language
You may also check:How to resolve the algorithm Hello world/Newline omission step by step in the J programming language
You may also check:How to resolve the algorithm Quaternion type step by step in the Scheme programming language