Solve day 15

2023/15_asciihash.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+import sys
+
+def asciihash(s):
+    h = 0
+    for char in s:
+        h = (h + ord(char)) * 17 % 256
+    return h
+
+def focus(steps):
+    boxes = [({}, []) for _ in range(256)]
+
+    for step in steps:
+        if step.endswith('-'):
+            label = step[:-1]
+            index, powers = boxes[asciihash(label)]
+            if label in index:
+                powers[index.pop(label)] = None
+        else:
+            label, power = step.split('=')
+            index, powers = boxes[asciihash(label)]
+            if label in index:
+                powers[index[label]] = int(power)
+            else:
+                index[label] = len(powers)
+                powers.append(int(power))
+
+    return sum(sum((b + 1) * (i + 1) * power
+                   for i, power in enumerate(filter(None, powers)))
+               for b, (_, powers) in enumerate(boxes))
+
+steps = next(sys.stdin).rstrip().split(',')
+print(sum(map(asciihash, steps)))
+print(focus(steps))