day 15 puzzle 1

src/day15/puzzle1.typ

@@ -0,0 +1,91 @@
+#import "/src/utils.typ": *
+
+#let WALL = "#"
+#let BOX = "O"
+#let BOT = "@"
+#let EMPTY = "."
+
+#let offsets = (
+  "^": (0, -1),
+  "<": (-1, 0),
+  "v": (0, 1),
+  ">": (1, 0)
+)
+
+#let compute-value(grid) = {
+  let total = 0
+  for (y, row) in grid.enumerate() {
+    for (x, type) in row.enumerate() {
+      if type == BOX {
+        total += y * 100 + x
+      }
+    }
+  }
+  return total
+}
+
+#let solve(input) = {
+  let (grid-data, move-data) = input.split("\n\n")
+  let grid = grid-data.split("\n").map(r => r.clusters())
+  let rows = ()
+  let cols = ()
+  
+  let w = grid.first().len()
+  let h = grid.len()
+  let bot-pos = none
+
+  for y in range(h) {
+    for x in range(w) {
+      let type = grid.at(y).at(x)
+      if type == BOT {
+        bot-pos = (x, y)
+        grid.at(y).at(x) = EMPTY
+        break
+      }
+    }
+    if bot-pos != none {
+      break
+    }
+  }
+  let (bot-x, bot-y) = bot-pos
+
+  let moves = move-data.replace("\n", "").clusters()
+  for (move-i, move) in moves.enumerate() {
+    let (dx, dy) = offsets.at(move)
+    let (x2, y2) = (bot-x + dx, bot-y + dy)
+    let type = grid.at(y2).at(x2)
+    if type == WALL {
+      continue
+    }
+    if type == EMPTY {
+      (bot-x, bot-y) = (x2, y2)
+      continue
+    }
+
+    let type2 = type
+    let (x3, y3) = (x2, y2)
+    while type2 == BOX {
+      x3 += dx
+      y3 += dy
+      type2 = grid.at(y3).at(x3)
+    }
+
+    if type2 == WALL {
+      continue
+    }
+    grid.at(y3).at(x3) = BOX
+    grid.at(y2).at(x2) = EMPTY
+    (bot-x, bot-y) = (x2, y2)
+  }
+
+  return compute-value(grid)
+}
+
+#show-puzzle(
+  15, 1,
+  solve,
+  example: (
+    "1": 2028,
+    "2": 10092
+  )
+)