day 9 puzzle 2

progress.yaml

@@ -15,4 +15,4 @@
 8:
   stars: 2
 9:
-  stars: 1
+  stars: 2

src/day9/puzzle2.typ

@@ -0,0 +1,69 @@
+#import "/src/utils.typ": *
+
+#let compute-checksum(blocks) = {
+  let total = 0
+  for (i0, l, id) in blocks {
+    total += id * range(i0, i0 + l).sum()
+  }
+  return total
+}
+
+#let insert(list, elmt) = {
+  for (i, elmt2) in list.enumerate() {
+    if elmt.first() < elmt2.first() {
+      list.insert(i, elmt)
+      return list
+    }
+  }
+  list.push(elmt)
+  return list
+}
+
+#let solve(input) = {
+  let blocks = ()
+  let holes = ()
+
+  let block-i = 0
+  let is-block = true
+  let pos = 0
+  for c in input {
+    let block = (pos, int(c))
+    if is-block {
+      block.push(block-i)
+      block-i += 1
+      blocks.push(block)
+    } else {
+      holes.push(block)
+    }
+    pos += int(c)
+    is-block = not is-block
+  }
+
+  let blocks2 = ()
+  for (bi, bl, bid) in blocks.rev() {
+    for (i, (hi, hl)) in holes.enumerate() {
+      if hi < bi and bl <= hl {
+        bi = hi
+        holes.at(i).first() += bl
+        holes.at(i).last() -= bl
+        break
+      }
+    }
+    blocks2.push((bi, bl, bid))
+  }
+  
+  return compute-checksum(blocks2)
+}
+
+#show-puzzle(
+  9, 2,
+  solve,
+  example: (
+    "1": 132,
+    "2": 2858
+  ),
+  only-example: true
+)
+
+// Too long to recompile everytime
+#show-result(6412390114238)