public static int SnakesAndLadders(int[][] board)
{
N = board.Length;
maxSquare = N * N;
visited = new int[maxSquare + 1];
for (int i = 0; i < visited.Length; i++)
{
visited[i] = -1;
}
Queue <int> q = new Queue <int>();
q.Enqueue(1);
visited[1] = 0; //roll dice starts from square 1
while (q.Count > 0)
{
int curr = q.Dequeue();
for (int i = 1; i <= 6; i++)
{
int next = curr + i;
if (next <= maxSquare)
{
SquareNode node = GetRowColumn(next);
if (board[node.Row][node.Col] != -1)
{
next = board[node.Row][node.Col];
}
if (visited[next] == -1) // this will make sure 1 has 0 distance and then cover scenario where snake takes back to 1
{
visited[next] = visited[curr] + 1;
q.Enqueue(next);//enqueue need to be done only if not visited earlier. if it is outisde of this if condiiton then it can go in infinite loop
}
if (next == maxSquare)
{
return(visited[next]);
}
}
}
}
return(visited[maxSquare]);
}
public int CompareTo(object obj)
{
if (obj == null)
{
throw new ArgumentNullException();
}
SquareNode other = obj as SquareNode;
if (this.Row == other.Row && this.Col == other.Col)
{
return(0);
}
else
{
return(-1);
}
}
public static List <SquareNode> GetNeighbours(SquareNode node, int rows, int cols)
{
List <SquareNode> neighbours = new List <SquareNode>();
int[][] moves = new int[][] { new int[] { 2, 1 }, new int[] { 2, -1 }, new int[] { -2, -1 }, new int[] { -2, 1 }, new int[] { 1, 2 }, new int[] { -1, 2 }, new int[] { 1, -2 }, new int[] { -1, -2 } };
for (int i = 0; i < 8; i++)
{
int newRow = node.Row + moves[i][0];
int newCol = node.Col + moves[i][1];
if (newRow < rows && newRow >= 0 && newCol < cols && newCol >= 0)
{
neighbours.Add(new SquareNode(newRow, newCol));//by default distance will be -1
}
}
return(neighbours);
}
//row col 0 indexed
public static int find_minimum_number_of_moves(int rows, int cols, int start_row, int start_col, int end_row, int end_col)
{
int moves = -1;
//create chess board
int[][] board = new int[rows][];
for (int i = 0; i < rows; i++)
{
board[i] = new int[cols];
}
SquareNode end = new SquareNode(end_row, end_col);
//BFS
Queue <SquareNode> q = new Queue <SquareNode>();
q.Enqueue(new SquareNode(start_row, start_col, 0)); //add to the q and set distance to 0
board[start_row][start_col] = 1; //mark the node visited by settingdistnace to 1
while (q.Count > 0)
{
//int currLevelSize = q.Count;
//for (int i = 0; i < currLevelSize; i++) //not required as we rely on parent's distance to calculate child's distance
//{
SquareNode node = q.Dequeue();
List <SquareNode> neighbours = GetNeighbours(node, rows, cols);
foreach (SquareNode n in neighbours)
{
if (board[n.Row][n.Col] == 0) //not visited
{
board[n.Row][n.Col] = 1;
n.Distance = node.Distance + 1;
q.Enqueue(n);
if (n.CompareTo(end) == 0)
{
return(n.Distance);
}
}
}
//}
}
return(moves);
}
