Day 15

aoc_cas/aoc2023/day15.py

@@ -0,0 +1,49 @@
+from typing import Iterator
+
+
+def parse_sequence(data: str) -> Iterator[str]:
+    for sequence in data.split(","):
+        yield sequence
+
+
+def hash(string: str) -> int:
+    val = 0
+    for c in string:
+        val += ord(c)
+        val *= 17
+        val %= 256
+    return val
+
+
+def part_a(data: str) -> int:
+    return sum(hash(seq) for seq in parse_sequence(data))
+
+
+def part_b(data: str) -> int:
+    boxes = [dict() for _ in range(256)]
+
+    for i, seq in enumerate(parse_sequence(data)):
+        if "=" in seq:
+            label, focal_length = seq.split("=")
+            box = boxes[hash(label)]
+            if label in box:
+                box[label][1] = int(focal_length)
+            else:
+                box[label] = [i, int(focal_length)]
+        else:
+            label = seq[:-1]
+            box = boxes[hash(label)]
+            box.pop(label, None)
+
+    focusing_power = 0
+    for box_num, box in enumerate(boxes, start=1):
+        lenses = sorted(box.values())
+        for lens_num, (_, focal_length) in enumerate(lenses, start=1):
+            focusing_power += box_num * lens_num * focal_length
+    return focusing_power
+
+
+if __name__ == "__main__":
+    from aoc_cas.util import solve_with_examples
+
+    solve_with_examples(year=2023, day=15)

tests/fixtures/2023/15.txt

@@ -0,0 +1,3 @@
+rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7
+1320
+145