started day 16 puzzle 1

res/examples/day16_1.txt

@@ -0,0 +1,15 @@
+###############
+#.......#....E#
+#.#.###.#.###.#
+#.....#.#...#.#
+#.###.#####.#.#
+#.#.#.......#.#
+#.#.#####.###.#
+#...........#.#
+###.#.#####.#.#
+#...#.....#.#.#
+#.#.#.###.#.#.#
+#.....#...#.#.#
+#.###.#.#.#.#.#
+#S..#.....#...#
+###############

res/examples/day16_2.txt

@@ -0,0 +1,17 @@
+#################
+#...#...#...#..E#
+#.#.#.#.#.#.#.#.#
+#.#.#.#...#...#.#
+#.#.#.#.###.#.#.#
+#...#.#.#.....#.#
+#.#.#.#.#.#####.#
+#.#...#.#.#.....#
+#.#.#####.#.###.#
+#.#.#.......#...#
+#.#.###.#####.###
+#.#.#...#.....#.#
+#.#.#.#####.###.#
+#.#.#.........#.#
+#.#.#.#########.#
+#S#.............#
+#################

src/day16/puzzle1.typ

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+#import "/src/utils.typ": *
+
+#let START = "S"
+#let END = "E"
+#let WALL = "#"
+#let EMPTY = "."
+
+#let offsets = (
+  (1, 0),
+  (0, 1),
+  (-1, 0),
+  (0, -1)
+)
+
+#let solve(input) = {
+  let grid = input.split("\n").map(l => l.clusters())
+  let w = grid.first().len()
+  let h = grid.len()
+
+  let (sx, sy) = (0, 0)
+  let (ex, ey) = (0, 0)
+  for y in range(h) {
+    for x in range(w) {
+      let c = grid.at(y).at(x)
+      if c == START {
+        (sx, sy) = (x, y)
+      } else if c == END {
+        (ex, ey) = (x, y)
+      }
+    }
+  }
+
+  let choices = ((sx, sy, 0, 0),)
+  let (x, y, dir, score) = (0, 0, 0, 0)
+  while choices.len() != 0 {
+    let min-score = calc.min(..choices.map(c => c.last()))
+    let i = choices.position(c => c.last() == min-score)
+    (x, y, dir, score) = choices.remove(i)
+    for (d, (dx, dy)) in offsets.enumerate() {
+      // Ignore backflips
+      if calc.abs(d - dir) == 2 {
+        continue
+      }
+      let (x2, y2) = (x + dx, y + dy)
+      let c = grid.at(y2).at(x2)
+      if c == WALL {
+        continue
+      }
+      let score2 = score + 1 + if d != dir {1000} else {0}
+      if c == END {
+        return score2
+      }
+      choices.push((x2, y2, d, score2))
+    }
+    break
+  }
+  return 0
+}
+
+#show-puzzle(
+  16, 1,
+  solve,
+  example: (
+    "1": 7036,
+    "2": 11048
+  )
+)