private List <PuzzleState> GenerateNextStates(PuzzleState state)
{
var nextStates = new List <PuzzleState>();
int emptyIndex = state.State.IndexOf(EmptyCell);
if ((emptyIndex - 1 >= 0) && (state.State[emptyIndex - 1] == RightFrog))
{
PuzzleState nextState = MakeMove(state, emptyIndex - 1, emptyIndex);
nextStates.Add(nextState);
}
if ((emptyIndex - 2 >= 0) && (state.State[emptyIndex - 2] == RightFrog))
{
PuzzleState nextState = MakeMove(state, emptyIndex - 2, emptyIndex);
nextStates.Add(nextState);
}
if ((emptyIndex + 1 < state.State.Length) && (state.State[emptyIndex + 1] == LeftFrog))
{
PuzzleState nextState = MakeMove(state, emptyIndex + 1, emptyIndex);
nextStates.Add(nextState);
}
if ((emptyIndex + 2 < state.State.Length) && (state.State[emptyIndex + 2] == LeftFrog))
{
PuzzleState nextState = MakeMove(state, emptyIndex + 2, emptyIndex);
nextStates.Add(nextState);
}
return(nextStates);
}
public void Solve()
{
Stack <PuzzleState> stack = new Stack <PuzzleState>();
stack.Push(this.initialState);
HashSet <PuzzleState> visited = new HashSet <PuzzleState>();
visited.Add(this.initialState);
while (stack.Count != 0)
{
PuzzleState currentState = stack.Pop();
if (currentState.State == targetState.State)
{
this.PrintSolution(currentState);
break;
}
List <PuzzleState> nextStates = GenerateNextStates(currentState);
foreach (var childState in nextStates)
{
if (!visited.Contains(childState))
{
childState.PreviousState = currentState;
stack.Push(childState);
visited.Add(childState);
}
}
}
}
private PuzzleState MakeMove(PuzzleState state, int i, int j)
{
char[] stateArr = state.State.ToCharArray();
char tempValue = stateArr[i];
stateArr[i] = stateArr[j];
stateArr[j] = tempValue;
return(new PuzzleState(new string(stateArr)));
}
private void PrintSolution(PuzzleState puzzleState)
{
Stack <PuzzleState> result = new Stack <PuzzleState>();
result.Push(puzzleState);
while (puzzleState.PreviousState != null)
{
puzzleState = puzzleState.PreviousState;
result.Push(puzzleState);
}
while (result.Count != 0)
{
Console.WriteLine(result.Pop());
}
}
public FrogsPuzzleSolver(int n)
{
this.n = n;
this.initialState = new PuzzleState(new string(RightFrog, n) + EmptyCell + new string(LeftFrog, n));
this.targetState = new PuzzleState(new string(LeftFrog, n) + EmptyCell + new string(RightFrog, n));
}
