2024 - Day 5 part 2

2024/5/5_2.py

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+#!/usr/bin/env python
+# 2024 - Advent Of Code 5 - part 2
+
+from math import floor
+
+# file = 'input_example.txt'
+file = 'input.txt'
+
+updates = []
+rules = {}
+update = 0
+with open(file, encoding="utf-8") as f:
+    for line in f.read().splitlines():
+        if line == '':
+            update = 1
+            continue
+        if update == 0:
+            before, after = line.split('|')
+            if int(before) in rules:
+                l = rules[int(before)]
+                l.append(int(after))
+                rules[int(before)] = l
+            else:
+                rules[int(before)] = [int(after)]
+        else:
+            updates.append([int(x) for x in line.split(',')])
+
+#print(f'{rules=}')
+#print(f'{updates=}')
+
+good_updates = []
+bad_updates = []
+for update in updates:
+    broken_rule = False
+    for num, page in enumerate(update):
+        if page in rules:
+            for p in rules[page]:
+                if p in update[0:num]:
+                    broken_rule = True
+                    break
+    if not broken_rule:
+        good_updates.append(update)
+    else:
+        bad_updates.append(update)
+
+for update in bad_updates:
+    working_update = update
+    for num, page in enumerate(working_update):
+        for u in working_update[:num]:
+            if page in rules:
+                if u in rules[page]:
+                    working_update.remove(u)
+                    working_update.insert(num, u)
+
+
+accum = 0
+print(f'# bad_updates {len(good_updates)}')
+for u in bad_updates:
+    accum += u[floor(len(u)/2)]
+
+print(f'{accum=}')