started day 21 puzzle 1

progress.yaml

@@ -37,4 +37,6 @@
 19:
   stars: 2
 20:
-  stars: 1
+  stars: 1
+21:
+  stars: 0

res/examples/day21.txt

@@ -0,0 +1,5 @@
+029A
+980A
+179A
+456A
+379A

src/day21/puzzle1.typ

@@ -0,0 +1,100 @@
+#import "/src/utils.typ": *
+
+#let nums = (
+  "7": (0, 0),
+  "8": (1, 0),
+  "9": (2, 0),
+  "4": (0, 1),
+  "5": (1, 1),
+  "6": (2, 1),
+  "1": (0, 2),
+  "2": (1, 2),
+  "3": (2, 2),
+  "0": (1, 3),
+  "A": (2, 3),
+)
+
+#let arrows = (
+  "^": (1, 0),
+  "A": (2, 0),
+  "<": (0, 1),
+  "v": (1, 1),
+  ">": (2, 1),
+)
+
+#let get-num-path(code) = {
+  let path = ""
+  let (x, y) = nums.at("A")
+  for char in code {
+    let (x2, y2) = nums.at(char)
+    let dy = y2 - y
+    let dx = x2 - x
+    let ver = if dy == 0 {
+      ""
+    } else {
+      (if dy < 0 {"^"} else {"v"}) * calc.abs(dy)
+    }
+    let hor = if dx == 0 {
+      ""
+    } else {
+      (if dx < 0 {"<"} else {">"}) * calc.abs(dx)
+    }
+    path += if y == 3 and x2 == 0 {
+      ver + hor
+    } else {
+      hor + ver
+    } + "A"
+    (x, y) = (x2, y2)
+  }
+  return path
+}
+
+#let get-dir-path(code) = {
+  let path = ""
+  let (x, y) = arrows.at("A")
+  for char in code {
+    let (x2, y2) = arrows.at(char)
+    let dy = y2 - y
+    let dx = x2 - x
+    let ver = if dy == 0 {
+      ""
+    } else {
+      (if dy < 0 {"^"} else {"v"}) * calc.abs(dy)
+    }
+    let hor = if dx == 0 {
+      ""
+    } else {
+      (if dx < 0 {"<"} else {">"}) * calc.abs(dx)
+    }
+    path += if x == 0 and dy < 0 {
+      hor + ver
+    } else {
+      ver + hor
+    } + "A"
+    (x, y) = (x2, y2)
+  }
+  return path
+}
+
+#let get-path(code) = {
+  let num-path = get-num-path(code)
+  let dir-path-1 = get-dir-path(num-path)
+  let dir-path-2 = get-dir-path(dir-path-1)
+  return dir-path-2
+}
+
+#let solve(input) = {
+  let codes = input.split("\n")
+  let total = 0
+  for code in codes {
+    let len = get-path(code).len()
+    let num = int(code.slice(0, code.len() - 1))
+    total += len * num
+  }
+  return total
+}
+#show-puzzle(
+  21, 1,
+  solve,
+  example: 126384
+)