public int QueryDistance(int x, int y)
{
if (x < 0 || x >= _width || y < 0 || y >= _height)
{
return(-1);
}
BFSCell cell = _grid[x, y];
return(cell.Distance);
}
private static Point BFS(Point s, int[][] board)
{
Queue <BFSCell> q = new Queue <BFSCell>();
int[] dr = new int[] { 1, 0, -1, 0 };
int[] dc = new int[] { 0, 1, 0, -1 };
for (int i = 0; i < 4; i++)
{
int nr = s.X + dr[i];
int nc = s.Y + dc[i];
if (nr >= 0 && nc >= 0 && nr < Rows && nc < Cols && board[nr][nc] == 0)
{
q.Enqueue(new BFSCell {
r = nr, c = nc, d = i, l = 0
});
}
}
while (q.Count > 0)
{
BFSCell p = q.Dequeue();
for (int i = 0; i < 4; i++)
{
if (Math.Abs(p.d - i) == 2)
{
continue;
}
int nr = p.r + dr[i];
int nc = p.c + dc[i];
if (nr >= 0 && nc >= 0 && nr < Rows && nc < Cols)
{
int nl = p.l;
if (p.d != i)
{
nl++;
}
if (nl > 2)
{
continue;
}
if (board[nr][nc] == 0)
{
BFSCell cell = new BFSCell {
r = nr, c = nc, d = i, l = nl
};
q.Enqueue(cell);
}
else if (board[nr][nc] == board[s.X][s.Y])
{
return(new Point(nr, nc));
}
}
}
}
return(new Point(-1, -1));
}
public void Reset()
{
for (int j = 0; j < _height; j++)
{
for (int i = 0; i < _width; i++)
{
BFSCell cell = _grid[i, j];
cell.Visited = false;
cell.CameFrom = null;
cell.Distance = -1;
}
}
}
public void SearchCharGrid(char[,] grid, char empty, int x, int y)
{
Reset();
Queue <BFSCell> frontier = new Queue <BFSCell>();
ProcessCell(grid, empty, frontier, null, x, y);
while (frontier.Any())
{
BFSCell current = frontier.Dequeue();
ProcessCell(grid, empty, frontier, current, current.X + 1, current.Y);
ProcessCell(grid, empty, frontier, current, current.X - 1, current.Y);
ProcessCell(grid, empty, frontier, current, current.X, current.Y + 1);
ProcessCell(grid, empty, frontier, current, current.X, current.Y - 1);
}
}
public BreadthFirstSearchGrid(int width, int height)
{
_grid = new BFSCell[width, height];
_width = width;
_height = height;
for (int j = 0; j < _height; j++)
{
for (int i = 0; i < _width; i++)
{
_grid[i, j] = new BFSCell {
X = i, Y = j,
};
}
}
}
private void ProcessCell(char[,] grid, char empty, Queue <BFSCell> frontier, BFSCell current, int nextX, int nextY)
{
if (nextX < 0 || nextX >= _width || nextY < 0 || nextY >= _height)
{
return;
}
if (grid[nextX, nextY] == empty || current == null)
{
BFSCell cell = _grid[nextX, nextY];
if (cell.Visited == false)
{
frontier.Enqueue(cell);
cell.Visited = true;
cell.Distance = (current?.Distance ?? -1) + 1;
cell.CameFrom = current;
}
}
}
