2024 day 5.

src/holt59/aoc/2024/day5.py

@@ -1,10 +1,49 @@
 import sys
+from collections import defaultdict
 
-lines = sys.stdin.read().splitlines()
+import networkx as nx
 
-answer_1 = ...
 
-answer_2 = ...
+def in_correct_order(update: list[int], requirements: dict[int, set[int]]) -> bool:
+    for i_value, value in enumerate(update):
+        if any(value_2 in requirements[value] for value_2 in update[i_value:]):
+            return False
+    return True
+
+
+def fix_order(update: list[int], requirements: dict[int, set[int]]) -> list[int]:
+    graph = nx.DiGraph()
+    graph.add_nodes_from(update)
+    graph.add_edges_from(
+        (v, k)
+        for k, vs in requirements.items()
+        for v in vs
+        if k in update and v in update
+    )
+
+    return list(nx.topological_sort(graph))
+
+
+part1, part2 = sys.stdin.read().split("\n\n")
+
+requirements: dict[int, set[int]] = defaultdict(set)
+for line in part1.splitlines():
+    v1, v2 = line.split("|")
+    requirements[int(v2)].add(int(v1))
+
+updates = [list(map(int, line.split(","))) for line in part2.splitlines()]
+
+answer_1 = sum(
+    update[len(update) // 2]
+    for update in updates
+    if in_correct_order(update, requirements)
+)
+
+answer_2 = sum(
+    fix_order(update, requirements)[len(update) // 2]
+    for update in updates
+    if not in_correct_order(update, requirements)
+)
 
 print(f"answer 1 is {answer_1}")
 print(f"answer 2 is {answer_2}")

src/holt59/aoc/inputs/tests/2024/day5.txt

@@ -0,0 +1,28 @@
+47|53
+97|13
+97|61
+97|47
+75|29
+61|13
+75|53
+29|13
+97|29
+53|29
+61|53
+97|53
+61|29
+47|13
+75|47
+97|75
+47|61
+75|61
+47|29
+75|13
+53|13
+
+75,47,61,53,29
+97,61,53,29,13
+75,29,13
+75,97,47,61,53
+61,13,29
+97,13,75,29,47