private PuzzleState MakeMove(PuzzleState puzzleState, int i, int j)
{
char[] stateArr = puzzleState.Position.ToCharArray();
char tempValue = stateArr[i];
stateArr[i] = stateArr[j];
stateArr[j] = tempValue;
return(new PuzzleState(new string(stateArr)));
}
private List <PuzzleState> GenerateNextStates(PuzzleState puzzleState)
{
var nextStates = new List <PuzzleState>();
int zeroIndex = puzzleState.Position.IndexOf('0');
int zeroX = zeroIndex / this.size;
int zeroY = zeroIndex % this.size;
if (zeroX > 0)
{
int targetIndex = zeroIndex - this.size;
PuzzleState nextState = this.MakeMove(puzzleState, zeroIndex, targetIndex);
nextState.Direction = DirectionDown;
nextStates.Add(nextState);
}
if (zeroX < this.size - 1)
{
int targetIndex = zeroIndex + this.size;
PuzzleState nextState = this.MakeMove(puzzleState, zeroIndex, targetIndex);
nextState.Direction = DirectionUp;
nextStates.Add(nextState);
}
if (zeroY > 0)
{
int targetIndex = zeroIndex - 1;
PuzzleState nextState = this.MakeMove(puzzleState, zeroIndex, targetIndex);
nextState.Direction = DirectionRight;
nextStates.Add(nextState);
}
if (zeroY < this.size - 1)
{
int targetIndex = zeroIndex + 1;
PuzzleState nextState = this.MakeMove(puzzleState, zeroIndex, targetIndex);
nextState.Direction = DirectionLeft;
nextStates.Add(nextState);
}
return(nextStates);
}
private int Heuristic(PuzzleState state)
{
int sum = 0;
for (int i = 0; i < this.targetState.Position.Length; i++)
{
char block = this.targetState.Position[i];
int x = state.Position.IndexOf(block) / this.size;
int y = state.Position.IndexOf(block) % this.size;
int targetX = this.targetState.Position.IndexOf(block) / this.size;
int targetY = this.targetState.Position.IndexOf(block) % this.size;
sum += this.ManhattanDistance(x, y, targetX, targetY);
}
return(sum);
}
private void PrintSolution(PuzzleState puzzleState)
{
Stack <PuzzleState> result = new Stack <PuzzleState>();
result.Push(puzzleState);
while (puzzleState.Parent != null)
{
puzzleState = puzzleState.Parent;
result.Push(puzzleState);
}
int steps = 0;
result.Pop();
while (result.Count != 0)
{
Console.WriteLine(result.Pop().Direction);
steps++;
}
Console.WriteLine("Total steps: {0}", steps);
}
public void Solve()
{
Console.WriteLine("Started solving the puzzle...");
HashSet <PuzzleState> exploredStates = new HashSet <PuzzleState>();
PriorityQueue <PuzzleState> unexploredStatesQueue = new PriorityQueue <PuzzleState>();
this.initialState.G = 0;
this.initialState.H = this.Heuristic(this.initialState);
this.initialState.F = this.initialState.H;
unexploredStatesQueue.Enqueue(this.initialState);
while (unexploredStatesQueue.Count != 0)
{
PuzzleState currentState = unexploredStatesQueue.Dequeue();
if (currentState.Position == this.targetState.Position)
{
this.PrintSolution(currentState);
break;
}
exploredStates.Add(currentState);
var nextStates = this.GenerateNextStates(currentState);
foreach (var childState in nextStates)
{
if (exploredStates.Contains(childState))
{
continue;
}
childState.G = currentState.G + 1;
childState.H = this.Heuristic(childState);
childState.F = childState.G + childState.H;
childState.Parent = currentState;
unexploredStatesQueue.Enqueue(childState);
}
}
}
public SlidingBlocksPuzzleSolver(int n, string initialPosition)
{
this.initialState = new PuzzleState(initialPosition);
this.targetState = new PuzzleState(this.InitializeTargetState(n));
this.size = (int)Math.Sqrt(n + 1);
}
