21: RPG Simulator 20XX

library(mistlecode)

To install `mistlecode` yourself, run `devtools::install_github('guslipkin/mistlecode')`.

 Also loading:  cipheR data.table dplyr purrr slider stringr tidyverse glue

shop <- 
  c(0, which(readLines("item_shop.txt") == "")) |>
  map(\(sk) {
    dt <- 
      fread("item_shop.txt", skip = sk) |>
      t() |>
      as.data.frame() |>
      janitor::row_to_names(1) |>
      as.list() |>
      map(\(x) { 
        x <- as.numeric(x)
        if (length(x) == 3) {
          names(x) <- c("cost", "damage", "armor")
        } else {
          names(x) <- c("modifier", "cost", "damage", "armor")
        }
        x 
      })
  }) |>
  `names<-`(c("weapons", "armor", "rings"))

boss <-
  readLines("input.txt") |>
  str_split(": ") |>
  map(\(x) {
    y <- as.numeric(x[2])
    names(y) <- x[1]
    as.list(y)
  }) |>
  unlist(recursive = FALSE) |>
  `names<-`(c("hp", "damage", "armor"))

Part 1

Ughhh. Not that difficult but I swapped the order of who goes first in my brain then suffered for a long time.

combinations <- function(shop, n) {
  n |>
    map(\(n) {
      if (n == 0) return(list("V0" = 0))
      shop |>
        length() |>
        combn(n) |>
        as.data.frame() |>
        as.list()
    }) |>
    unlist(recursive = FALSE)
}
weapons <- combinations(shop$weapons, 1)
armor <- combinations(shop$armor, 0:1)
rings <- combinations(shop$rings, 0:2)

expand.grid(
  "w" = seq_along(weapons),
  "a" = seq_along(armor),
  "r" = seq_along(rings)
)|>
  pmap(\(w, a, r) {
    w <- as.list(shop$weapons[[weapons[[w]]]])
    a <- if (armor[[a]] == 0) list("cost" = 0, "armor" = 0) else as.list(shop$armor[[armor[[a]]]])
    r <- if (any(rings[[r]] == 0)) list(list("modifier" = 0, "cost" = 0, "damage" = 0, "armor" = 0)) else map(rings[[r]], ~ as.list(shop$rings[[.x]]))
    damage <- w$damage + sum(map_dbl(r, ~ .x$damage), na.rm = TRUE)
    armor <- a$armor + sum(map_dbl(r, ~ .x$armor), na.rm = TRUE)
    hp <- 100
    boss_hp <- boss$hp
    repeat {
      my_damage <- damage - boss$armor
      boss_hp <- if (my_damage <= 0) { boss_hp - 1 } else { boss_hp - my_damage }
      if (boss_hp <= 0) { break }
      boss_damage <- boss$damage - armor
      hp <- if (boss_damage <= 0) { hp - 1 } else { hp - boss_damage }
      if (hp <= 0) { break }
    }
    if (hp > 0 & boss_hp <= 0) {
      return(w$cost + a$cost + sum(map_int(r, ~ .x$cost)))
    } else {
      return(NA_integer_)
    }
  }) |>
  unlist() |>
  min(na.rm = TRUE)

[1] 78

Part 2

Classic Advent. smh. But super easy.

expand.grid(
  "w" = seq_along(weapons),
  "a" = seq_along(armor),
  "r" = seq_along(rings)
)|>
  pmap(\(w, a, r) {
    w <- as.list(shop$weapons[[weapons[[w]]]])
    a <- if (armor[[a]] == 0) list("cost" = 0, "armor" = 0) else as.list(shop$armor[[armor[[a]]]])
    r <- if (any(rings[[r]] == 0)) list(list("modifier" = 0, "cost" = 0, "damage" = 0, "armor" = 0)) else map(rings[[r]], ~ as.list(shop$rings[[.x]]))
    damage <- w$damage + sum(map_dbl(r, ~ .x$damage), na.rm = TRUE)
    armor <- a$armor + sum(map_dbl(r, ~ .x$armor), na.rm = TRUE)
    hp <- 100
    boss_hp <- boss$hp
    repeat {
      my_damage <- damage - boss$armor
      boss_hp <- if (my_damage <= 0) { boss_hp - 1 } else { boss_hp - my_damage }
      if (boss_hp <= 0) { break }
      boss_damage <- boss$damage - armor
      hp <- if (boss_damage <= 0) { hp - 1 } else { hp - boss_damage }
      if (hp <= 0) { break }
    }
    if (hp <= 0 & boss_hp > 0) {
      return(w$cost + a$cost + sum(map_int(r, ~ .x$cost)))
    } else {
      return(NA_integer_)
    }
  }) |>
  unlist() |>
  max(na.rm = TRUE)

[1] 148