2022 Day 23

Author: mimmackk

2022/R/day23.qmd

@@ -0,0 +1,138 @@
+---
+title: "Day 23"
+date: 2022-12-23
+author:
+  name: https://adventofcode.com/2022/day/23
+  url: https://adventofcode.com/2022/day/23
+---
+
+## Setup
+
+```{r setup}
+
+# Libraries
+library(tidyverse)
+
+# Read input from file
+input <- read_lines("../input/day23.txt", skip_empty_rows = TRUE) |> 
+  enframe(name = "row") |> 
+  mutate(value = map(value, ~ enframe(str_split_1(.x, ""), name = "col"))) |> 
+  unnest(value)
+
+```
+
+## Part 1
+
+Convert map to a list of positions for each elf, using complex numbers to store 2D coords:
+
+```{r}
+
+elves <- input |> 
+  filter(value == "#") |> 
+  mutate(z = complex(real = col, imaginary = row)) |> 
+  pull(z)
+
+```
+
+Define function to move elves in each round:
+
+```{r}
+
+cardinal_dirs <- c(
+  n  =  0 - 1i,
+  s  =  0 + 1i,
+  w  = -1 + 0i,
+  e  =  1 + 0i,
+  nw = -1 - 1i,
+  ne =  1 - 1i,
+  sw = -1 + 1i,
+  se =  1 + 1i
+)
+
+adjacent_dirs <- list(
+  n = c("n", "nw", "ne"),
+  s = c("s", "sw", "se"),
+  w = c("w", "nw", "sw"),
+  e = c("e", "ne", "se")
+)
+
+move_elves <- function(elves, round_num) {
+
+  # Determine which neighboring cells are occupied
+  neighbors <- map(cardinal_dirs, \(dir) elves + dir)
+  occupied  <- map(neighbors, ~ .x %in% elves)
+  
+  # Determine which n/s/w/e moves are valid
+  valid <- map(adjacent_dirs, \(dir_set) {
+    dir_set |> 
+      map(~!occupied[[.x]]) |> 
+      reduce(`&`)
+  })
+  
+  # Re-order the n/s/w/e priority according to the current round number
+  valid <- valid[(1:4 + round_num - 2) %% 4 + 1]
+  
+  # For all elves not surrounded by empty cells, determine their proposed move
+  all_borders_empty <- reduce(valid, `&`)
+  proposals <- valid |> 
+    imap(\(vec, dir) case_when(vec ~ neighbors[[dir]])) |>
+    pmap(
+      ~ c(discard(c(..1, ..2, ..3, ..4), is.na), NA) |> 
+        head(1)
+    ) |> 
+    unlist() |> 
+    modify_if(all_borders_empty, ~ NA)
+  
+  # Nullify any colliding proposed moves
+  collisions <- na.omit(proposals)[duplicated(na.omit(proposals))]
+  movements <- if_else(proposals %in% collisions, NA, proposals)
+  
+  # Return the new elf coordinates
+  coalesce(movements, elves)
+}
+
+```
+
+Define a function to compute the area of the bounding box then subtract away the number of elves:
+
+```{r}
+
+n_empty_tiles <- function(elves) {
+  height <- 1 + diff(range(Im(elves)))
+  width  <- 1 + diff(range(Re(elves)))
+  
+  height * width - length(elves)
+}
+
+```
+
+Run 10 rounds on puzzle input:
+
+```{r}
+
+reduce(1:10, move_elves, .init = elves) |> 
+  n_empty_tiles()
+
+```
+
+## Part 2
+
+Run until no further movements occur:
+
+```{r}
+
+i <- 1
+cur_elves <- elves
+
+repeat {
+  new_elves <- move_elves(cur_elves, i)
+  
+  if (all(new_elves == cur_elves)) break
+  
+  cur_elves <- new_elves
+  i <- i + 1
+}
+
+i
+
+```

_freeze/2022/R/day23/execute-results/html.json

@@ -0,0 +1,15 @@
+{
+  "hash": "55a4440ee28c9580f6107d1afd9797f2",
+  "result": {
+    "engine": "knitr",
+    "markdown": "---\ntitle: \"Day 23\"\ndate: 2022-12-23\nauthor:\n  name: https://adventofcode.com/2022/day/23\n  url: https://adventofcode.com/2022/day/23\n---\n\n\n\n\n## Setup\n\n\n\n\n::: {.cell}\n\n```{.r .cell-code}\n# Libraries\nlibrary(tidyverse)\n\n# Read input from file\ninput <- read_lines(\"../input/day23.txt\", skip_empty_rows = TRUE) |> \n  enframe(name = \"row\") |> \n  mutate(value = map(value, ~ enframe(str_split_1(.x, \"\"), name = \"col\"))) |> \n  unnest(value)\n```\n:::\n\n\n\n\n## Part 1\n\nConvert map to a list of positions for each elf, using complex numbers to store 2D coords:\n\n\n\n\n::: {.cell}\n\n```{.r .cell-code}\nelves <- input |> \n  filter(value == \"#\") |> \n  mutate(z = complex(real = col, imaginary = row)) |> \n  pull(z)\n```\n:::\n\n\n\n\nDefine function to move elves in each round:\n\n\n\n\n::: {.cell}\n\n```{.r .cell-code}\ncardinal_dirs <- c(\n  n  =  0 - 1i,\n  s  =  0 + 1i,\n  w  = -1 + 0i,\n  e  =  1 + 0i,\n  nw = -1 - 1i,\n  ne =  1 - 1i,\n  sw = -1 + 1i,\n  se =  1 + 1i\n)\n\nadjacent_dirs <- list(\n  n = c(\"n\", \"nw\", \"ne\"),\n  s = c(\"s\", \"sw\", \"se\"),\n  w = c(\"w\", \"nw\", \"sw\"),\n  e = c(\"e\", \"ne\", \"se\")\n)\n\nmove_elves <- function(elves, round_num) {\n\n  # Determine which neighboring cells are occupied\n  neighbors <- map(cardinal_dirs, \\(dir) elves + dir)\n  occupied  <- map(neighbors, ~ .x %in% elves)\n  \n  # Determine which n/s/w/e moves are valid\n  valid <- map(adjacent_dirs, \\(dir_set) {\n    dir_set |> \n      map(~!occupied[[.x]]) |> \n      reduce(`&`)\n  })\n  \n  # Re-order the n/s/w/e priority according to the current round number\n  valid <- valid[(1:4 + round_num - 2) %% 4 + 1]\n  \n  # For all elves not surrounded by empty cells, determine their proposed move\n  all_borders_empty <- reduce(valid, `&`)\n  proposals <- valid |> \n    imap(\\(vec, dir) case_when(vec ~ neighbors[[dir]])) |>\n    pmap(\n      ~ c(discard(c(..1, ..2, ..3, ..4), is.na), NA) |> \n        head(1)\n    ) |> \n    unlist() |> \n    modify_if(all_borders_empty, ~ NA)\n  \n  # Nullify any colliding proposed moves\n  collisions <- na.omit(proposals)[duplicated(na.omit(proposals))]\n  movements <- if_else(proposals %in% collisions, NA, proposals)\n  \n  # Return the new elf coordinates\n  coalesce(movements, elves)\n}\n```\n:::\n\n\n\n\nDefine a function to compute the area of the bounding box then subtract away the number of elves:\n\n\n\n\n::: {.cell}\n\n```{.r .cell-code}\nn_empty_tiles <- function(elves) {\n  height <- 1 + diff(range(Im(elves)))\n  width  <- 1 + diff(range(Re(elves)))\n  \n  height * width - length(elves)\n}\n```\n:::\n\n\n\n\nRun 10 rounds on puzzle input:\n\n\n\n\n::: {.cell}\n\n```{.r .cell-code}\nreduce(1:10, move_elves, .init = elves) |> \n  n_empty_tiles()\n```\n\n::: {.cell-output .cell-output-stdout}\n\n```\n[1] 3996\n```\n\n\n:::\n:::\n\n\n\n\n## Part 2\n\nRun until no further movements occur:\n\n\n\n\n::: {.cell}\n\n```{.r .cell-code}\ni <- 1\ncur_elves <- elves\n\nrepeat {\n  new_elves <- move_elves(cur_elves, i)\n  \n  if (all(new_elves == cur_elves)) break\n  \n  cur_elves <- new_elves\n  i <- i + 1\n}\n\ni\n```\n\n::: {.cell-output .cell-output-stdout}\n\n```\n[1] 908\n```\n\n\n:::\n:::\n",
+    "supporting": [],
+    "filters": [
+      "rmarkdown/pagebreak.lua"
+    ],
+    "includes": {},
+    "engineDependencies": {},
+    "preserve": {},
+    "postProcess": true
+  }
+}

docs/2022/R/day01.html

@@ -436,6 +436,12 @@ <h1 class="quarto-secondary-nav-title">Day 1</h1>
   <a href="../../2022/R/day22.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text">Day 22</span></a>
   </div>
+</li>
+          <li class="sidebar-item">
+  <div class="sidebar-item-container"> 
+  <a href="../../2022/R/day23.html" class="sidebar-item-text sidebar-link">
+ <span class="menu-text">Day 23</span></a>
+  </div>
 </li>
       </ul>
   </li>

docs/2022/R/day02.html

@@ -436,6 +436,12 @@ <h1 class="quarto-secondary-nav-title">Day 2</h1>
   <a href="../../2022/R/day22.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text">Day 22</span></a>
   </div>
+</li>
+          <li class="sidebar-item">
+  <div class="sidebar-item-container"> 
+  <a href="../../2022/R/day23.html" class="sidebar-item-text sidebar-link">
+ <span class="menu-text">Day 23</span></a>
+  </div>
 </li>
       </ul>
   </li>

docs/2022/R/day03.html

@@ -436,6 +436,12 @@ <h1 class="quarto-secondary-nav-title">Day 3</h1>
   <a href="../../2022/R/day22.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text">Day 22</span></a>
   </div>
+</li>
+          <li class="sidebar-item">
+  <div class="sidebar-item-container"> 
+  <a href="../../2022/R/day23.html" class="sidebar-item-text sidebar-link">
+ <span class="menu-text">Day 23</span></a>
+  </div>
 </li>
       </ul>
   </li>

docs/2022/R/day04.html

@@ -436,6 +436,12 @@ <h1 class="quarto-secondary-nav-title">Day 4</h1>
   <a href="../../2022/R/day22.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text">Day 22</span></a>
   </div>
+</li>
+          <li class="sidebar-item">
+  <div class="sidebar-item-container"> 
+  <a href="../../2022/R/day23.html" class="sidebar-item-text sidebar-link">
+ <span class="menu-text">Day 23</span></a>
+  </div>
 </li>
       </ul>
   </li>

docs/2022/R/day05.html

@@ -436,6 +436,12 @@ <h1 class="quarto-secondary-nav-title">Day 5</h1>
   <a href="../../2022/R/day22.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text">Day 22</span></a>
   </div>
+</li>
+          <li class="sidebar-item">
+  <div class="sidebar-item-container"> 
+  <a href="../../2022/R/day23.html" class="sidebar-item-text sidebar-link">
+ <span class="menu-text">Day 23</span></a>
+  </div>
 </li>
       </ul>
   </li>

docs/2022/R/day06.html

@@ -436,6 +436,12 @@ <h1 class="quarto-secondary-nav-title">Day 6</h1>
   <a href="../../2022/R/day22.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text">Day 22</span></a>
   </div>
+</li>
+          <li class="sidebar-item">
+  <div class="sidebar-item-container"> 
+  <a href="../../2022/R/day23.html" class="sidebar-item-text sidebar-link">
+ <span class="menu-text">Day 23</span></a>
+  </div>
 </li>
       </ul>
   </li>

docs/2022/R/day07.html

@@ -436,6 +436,12 @@ <h1 class="quarto-secondary-nav-title">Day 7</h1>
   <a href="../../2022/R/day22.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text">Day 22</span></a>
   </div>
+</li>
+          <li class="sidebar-item">
+  <div class="sidebar-item-container"> 
+  <a href="../../2022/R/day23.html" class="sidebar-item-text sidebar-link">
+ <span class="menu-text">Day 23</span></a>
+  </div>
 </li>
       </ul>
   </li>

docs/2022/R/day08.html

@@ -436,6 +436,12 @@ <h1 class="quarto-secondary-nav-title">Day 8</h1>
   <a href="../../2022/R/day22.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text">Day 22</span></a>
   </div>
+</li>
+          <li class="sidebar-item">
+  <div class="sidebar-item-container"> 
+  <a href="../../2022/R/day23.html" class="sidebar-item-text sidebar-link">
+ <span class="menu-text">Day 23</span></a>
+  </div>
 </li>
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