public static int MinimumMoves(int[][] grid)
{
// 0 is unvisited, 1 is visited horizontally, 2 vertically, 3 both.
int[,] visited = new int[grid.Length, grid[0].Length];
int[,] shortestPathHorizontal = new int[grid.Length, grid[0].Length];
int[,] shortestPathVertical = new int[grid.Length, grid[0].Length];
for (int i = 0; i < shortestPathHorizontal.GetLength(0); i++)
{
for (int j = 0; j < shortestPathHorizontal.GetLength(1); j++)
{
shortestPathHorizontal[i, j] = int.MaxValue;
shortestPathVertical[i, j] = int.MaxValue;
}
}
SnakeCoordinate start = new SnakeCoordinate(0, 1, true);
Queue <SnakeCoordinate> queue = new Queue <SnakeCoordinate>();
queue.Enqueue(start);
visited[0, 1] = 1;
shortestPathHorizontal[0, 1] = 0;
while (queue.Count != 0)
{
var coord = queue.Dequeue();
if (coord.IsHorizontal)
{
MoveHorizontal(grid, queue, coord, shortestPathHorizontal, shortestPathVertical, visited);
}
else
{
MoveVertical(grid, queue, coord, shortestPathHorizontal, shortestPathVertical, visited);
}
}
if (shortestPathHorizontal[grid.Length - 1, grid.Length - 1] == int.MaxValue)
{
return(-1);
}
return(shortestPathHorizontal[grid.Length - 1, grid.Length - 1]);
}
private static void MoveHorizontal(int[][] grid, Queue <SnakeCoordinate> queue, SnakeCoordinate coord, int[,] shortestPathHorizontal, int[,] shortestPathVertical, int[,] visited)
{
// Move right
int nxHead = coord.I;
int nyHead = coord.J + 1;
int nxBody = coord.I;
int nyBody = coord.J;
if (nyHead >= 0 && nyHead < grid.Length && (visited[nxHead, nyHead] == 0 || visited[nxHead, nyHead] == 2) && grid[nxHead][nyHead] == 0)
{
SnakeCoordinate coordinate = new SnakeCoordinate(nxHead, nyHead, true);
queue.Enqueue(coordinate);
if (shortestPathHorizontal[coord.I, coord.J] + 1 < shortestPathHorizontal[nxHead, nyHead])
{
shortestPathHorizontal[nxHead, nyHead] = shortestPathHorizontal[coord.I, coord.J] + 1;
}
if (visited[nxHead, nyHead] == 0)
{
visited[nxHead, nyHead] = 1;
}
else
{
visited[nxHead, nyHead] = 3;
}
}
// Move down
nxHead = coord.I + 1;
nyHead = coord.J;
nxBody = coord.I + 1;
nyBody = coord.J - 1;
if (nxHead >= 0 && nxHead < grid.Length && (visited[nxHead, nyHead] == 0 || visited[nxHead, nyHead] == 2) && grid[nxHead][nyHead] == 0 && grid[nxBody][nyBody] == 0)
{
SnakeCoordinate coordinate = new SnakeCoordinate(nxHead, nyHead, true);
queue.Enqueue(coordinate);
if (shortestPathHorizontal[coord.I, coord.J] + 1 < shortestPathHorizontal[nxHead, nyHead])
{
shortestPathHorizontal[nxHead, nyHead] = shortestPathHorizontal[coord.I, coord.J] + 1;
}
if (visited[nxHead, nyHead] == 0)
{
visited[nxHead, nyHead] = 1;
}
else
{
visited[nxHead, nyHead] = 3;
}
}
// Rotate clockwise
nxHead = coord.I + 1;
nyHead = coord.J - 1;
nxBody = coord.I;
nyBody = coord.J - 1;
if (nxHead >= 0 && nxHead < grid.Length && nyHead + 1 >= 0 && nyHead + 1 < grid.Length && (visited[nxHead, nyHead] == 0 || visited[nxHead, nyHead] == 1) && grid[nxHead][nyHead] == 0 && grid[nxHead][nyHead + 1] == 0)
{
SnakeCoordinate coordinate = new SnakeCoordinate(nxHead, nyHead, false);
queue.Enqueue(coordinate);
if (shortestPathHorizontal[coord.I, coord.J] + 1 < shortestPathVertical[nxHead, nyHead])
{
shortestPathVertical[nxHead, nyHead] = shortestPathHorizontal[coord.I, coord.J] + 1;
}
if (visited[nxHead, nyHead] == 0)
{
visited[nxHead, nyHead] = 2;
}
else
{
visited[nxHead, nyHead] = 3;
}
}
}
