R/distance.R

In Ziegelsteintom/rmazing: Algorithms for Different Kinds of Perfect Mazes

#' Distance
#'
#' Calculate the distance for any cell from the bottom left cell
#'
#' @param maze a maze object
#' @param start starting point
#'
#' @return returns a matrix with numbers as distances
#' @export
#'
#' @examples
#' maze <- makeMazeRecursiveBacktracker()
#' distance(maze)

distance <- function(maze, start = NULL){

  w <- attributes(maze)$width
  h <- attributes(maze)$height
  if(is.null(start)){start <- attributes(maze)$start}

  # Initialize distance matrix
  dist_mat <- matrix(0, nrow = h, ncol = w)

  row_nr <- coord_from_list_nr(start, w, h)[1]
  col_nr <- coord_from_list_nr(start, w, h)[2]
  # For now the starting point is fixed with 1
  dist_mat[row_nr, col_nr] <- 1

  # Initialize distance with 1
  k <- 1

  # Bruteforce search
  while(any(dist_mat == 0)){
    ind <- which(dist_mat == k, arr.ind = TRUE)
      for(i in 1:nrow(ind)){

        # ??
        nr <- list_nr(ind[i,2], h + 1 -ind[i,1], width = w)

        # 1N, 2E, 3S, 4W
        if(maze[nr, 1] == 0 && dist_mat[ind[i,1] - 1, ind[i,2]] == 0)
            dist_mat[h + 1 - maze[nr, "y"] - 1, maze[nr, "x"] + 0] <- k + 1

        if(maze[nr, 2] == 0 && dist_mat[ind[i,1], ind[i,2] + 1] == 0)
            dist_mat[h + 1 - maze[nr, "y"] + 0, maze[nr, "x"] + 1] <- k + 1

        if(maze[nr, 3] == 0 && dist_mat[ind[i,1] + 1, ind[i,2]] == 0)
             dist_mat[h + 1 - maze[nr, "y"] + 1, maze[nr, "x"] + 0] <- k + 1

        if(maze[nr, 4] == 0 && dist_mat[ind[i,1], ind[i,2] - 1] == 0)
             dist_mat[h + 1 - maze[nr, "y"] + 0, maze[nr, "x"] - 1] <- k + 1

      }
    k <- k + 1

  }

  return(structure(dist_mat, class = "distance", width = w, height = h, start = start))
}