R/snakes_and_ladders.R

In jr-packages/efficientTutorial: Efficient R Programming

check_snake = function(square) {
  switch(as.character(square),
         "16" = 6, "49" = 12, "47" = 26, "56" = 48, "62" = 19,
         "64" = 60, "87" = 24, "93" = 73, "96" = 76, "98" = 78,
         square)
}

check_ladders = function(square) {
  switch(as.character(square),
         "1" = 38,  "4" = 14, "9" = 31, "28" = 84, "37" = 43,
         "51" = 67, "69" = 91, "79" = 100,
         square)
}

move = function(square, die) {
  square = square + die
  if (square > 100)  square = 200 - square
  square
}

#' Snakes and Ladders
#'
#' A simple game of snakes and ladders.
#' @param i A dummy argument needed for the parallel interface.
#' @return Number of rolls needed to win.
#' @export
snakes_ladders = function(i = 1) {
  square = 1
  no_of_rolls = 0
  while (square < 100) {
    die = 6 # Keep moving if you get a 6!
    while (die == 6) {
      die = sample(1:6, 1)
      square = move(square, die)
      no_of_rolls = no_of_rolls + 1
    }
    square = check_snake(square)
    square = check_ladders(square)
  }
  no_of_rolls
}