day 6 puzzle 1

progress.yaml

@@ -7,4 +7,6 @@
 4:
   stars: 2
 5:
-  stars: 2
+  stars: 2
+6:
+  stars: 1

res/examples/day6.txt

@@ -0,0 +1,10 @@
+....#.....
+.........#
+..........
+..#.......
+.......#..
+..........
+.#..^.....
+........#.
+#.........
+......#...

src/day6/puzzle1.typ

@@ -0,0 +1,79 @@
+#import "/src/utils.typ": *
+
+#let offsets = (
+  (0, -1),
+  (1, 0),
+  (0, 1),
+  (-1, 0)
+)
+
+#let in-grid(x, y, w, h) = {
+  return 0 <= x and x < w and 0 <= y and y < h
+}
+
+#let solve(input) = {
+  let grid = input.split("\n").map(l => l.clusters())
+
+  let w = grid.first().len()
+  let h = grid.len()
+
+  let ox = 0
+  let oy = 0
+  let found-start = false
+  for y in range(h) {
+    for x in range(h) {
+      if grid.at(y).at(x) == "^" {
+        ox = x
+        oy = y
+        found-start = true
+        break
+      }
+    }
+    if found-start {
+      break
+    }
+  }
+
+  grid.at(oy).at(ox) = "v"
+
+  let x = ox
+  let y = oy
+  let dir = 0
+  let count = 1
+  let (dx, dy) = offsets.at(dir)
+  while in-grid(x, y, w, h) {
+    if grid.at(y).at(x) != "v" {
+      grid.at(y).at(x) = "v"
+      count += 1
+    }
+
+    let x2 = x + dx
+    let y2 = y + dy
+    if not in-grid(x2, y2, w, h) {
+      break
+    }
+
+    for _ in range(4) {
+      let next = grid.at(y2).at(x2)
+
+      if next == "#" {
+        dir = calc.rem(dir + 1, 4)
+        (dx, dy) = offsets.at(dir)
+        x2 = x + dx
+        y2 = y + dy
+      } else {
+        break
+      }
+    }
+
+    x = x2
+    y = y2
+  }
+  return count
+}
+
+#show-puzzle(
+  6, 1,
+  solve,
+  example: 41
+)