day02.R

#' Day 02: Rock Paper Scissors
#'
#' [Rock Paper Scissors](https://adventofcode.com/2022/day/2)
#'
#' @name day02
#' @rdname day02
#' @details
#'
#' **Part One**
#'
#' The Elves begin to set up camp on the beach. To decide whose tent gets
#' to be closest to the snack storage, a giant [Rock Paper
#' Scissors](https://en.wikipedia.org/wiki/Rock_paper_scissors){target="_blank"}
#' tournament is already in progress.
#'
#' Rock Paper Scissors is a game between two players. Each game contains
#' many rounds; in each round, the players each simultaneously choose one
#' of Rock, Paper, or Scissors using a hand shape. Then, a winner for that
#' round is selected: Rock defeats Scissors, Scissors defeats Paper, and
#' Paper defeats Rock. If both players choose the same shape, the round
#' instead ends in a draw.
#'
#' Appreciative of your help yesterday, one Elf gives you an *encrypted
#' strategy guide* (your puzzle input) that they say will be sure to help
#' you win. \"The first column is what your opponent is going to play: `A`
#' for Rock, `B` for Paper, and `C` for Scissors. The second column\--\"
#' Suddenly, the Elf is called away to help with someone\'s tent.
#'
#' The second column, [you reason]{title="Why do you keep guessing?!"},
#' must be what you should play in response: `X` for Rock, `Y` for Paper,
#' and `Z` for Scissors. Winning every time would be suspicious, so the
#' responses must have been carefully chosen.
#'
#' The winner of the whole tournament is the player with the highest score.
#' Your *total score* is the sum of your scores for each round. The score
#' for a single round is the score for the *shape you selected* (1 for
#' Rock, 2 for Paper, and 3 for Scissors) plus the score for the *outcome
#' of the round* (0 if you lost, 3 if the round was a draw, and 6 if you
#' won).
#'
#' Since you can\'t be sure if the Elf is trying to help you or trick you,
#' you should calculate the score you would get if you were to follow the
#' strategy guide.
#'
#' For example, suppose you were given the following strategy guide:
#'
#'     A Y
#'     B X
#'     C Z
#'
#' This strategy guide predicts and recommends the following:
#'
#' -   In the first round, your opponent will choose Rock (`A`), and you
#'     should choose Paper (`Y`). This ends in a win for you with a score
#'     of *8* (2 because you chose Paper + 6 because you won).
#' -   In the second round, your opponent will choose Paper (`B`), and you
#'     should choose Rock (`X`). This ends in a loss for you with a score
#'     of *1* (1 + 0).
#' -   The third round is a draw with both players choosing Scissors,
#'     giving you a score of 3 + 3 = *6*.
#'
#' In this example, if you were to follow the strategy guide, you would get
#' a total score of *`15`* (8 + 1 + 6).
#'
#' *What would your total score be if everything goes exactly according to
#' your strategy guide?*
#'
#' **Part Two**
#'
#' The Elf finishes helping with the tent and sneaks back over to you.
#' \"Anyway, the second column says how the round needs to end: `X` means
#' you need to lose, `Y` means you need to end the round in a draw, and `Z`
#' means you need to win. Good luck!\"
#'
#' The total score is still calculated in the same way, but now you need to
#' figure out what shape to choose so the round ends as indicated. The
#' example above now goes like this:
#'
#' -   In the first round, your opponent will choose Rock (`A`), and you
#'     need the round to end in a draw (`Y`), so you also choose Rock. This
#'     gives you a score of 1 + 3 = *4*.
#' -   In the second round, your opponent will choose Paper (`B`), and you
#'     choose Rock so you lose (`X`) with a score of 1 + 0 = *1*.
#' -   In the third round, you will defeat your opponent\'s Scissors with
#'     Rock for a score of 1 + 6 = *7*.
#'
#' Now that you\'re correctly decrypting the ultra top secret strategy
#' guide, you would get a total score of *`12`*.
#'
#' Following the Elf\'s instructions for the second column, *what would
#' your total score be if everything goes exactly according to your
#' strategy guide?*
#'
#' @param x some data
#' @return For Part One, `f02a(x)` returns .... For Part Two,
#'   `f02b(x)` returns ....
#' @export
#' @examples
#' f02a(example_data_02())
#' f02b()
f02a <- function(x) {
  x <- gsub(" ", "", x)
  sum(sapply(x, f02_helper))
}


#' @rdname day02
#' @export
f02b <- function(x) {
  x <- gsub(" ", "", x)
  sum(sapply(x, f02b_helper))
}


f02_helper <- function(x) {
  switch(x,
         AX = 1 + 3,
         AY = 2 + 6,
         AZ = 3 + 0,
         BX = 1 + 0,
         BY = 2 + 3,
         BZ = 3 + 6,
         CX = 1 + 6,
         CY = 2 + 0,
         CZ = 3 + 3)
}

f02b_helper <- function(x) {
  switch(x,
         AX = 3 + 0,
         AY = 1 + 3,
         AZ = 2 + 6,
         BX = 1 + 0,
         BY = 2 + 3,
         BZ = 3 + 6,
         CX = 2 + 0,
         CY = 3 + 3,
         CZ = 1 + 6)
}


#' @param example Which example data to use (by position or name). Defaults to
#'   1.
#' @rdname day02
#' @export
example_data_02 <- function(example = 1) {
  l <- list(
    a = c("A Y",
          "B X",
          "C Z")
  )
  l[[example]]
}