diff --git a/2024/day05/day05.py b/2024/day05/day05.py
new file mode 100644
index 0000000..260d01b
--- /dev/null
+++ b/2024/day05/day05.py
@@ -0,0 +1,120 @@
+from collections import defaultdict
+
+
+def day5(input: str, part: int) -> int:
+    split_input = input.split("\n\n")
+
+    reversed_graph: defaultdict[int, list[int]] = defaultdict(list)
+    for line in split_input[0].splitlines():
+        rule_parts = line.split("|")
+        X, Y = int(rule_parts[0]), int(rule_parts[1])
+        reversed_graph[Y].append(X)
+
+    updates: list[list[int]] = [
+        [int(x) for x in line.split(",")] for line in split_input[1].splitlines()
+    ]
+    part1_ans: int = 0
+
+    # for part 2
+    invalid_updates: list[list[int]] = []
+
+    for update in updates:
+        # assuming there are no repeat updates...
+        seen_set: set[int] = set()
+        disallowed_set: set[int] = set()
+        is_valid = True
+
+        for num in update:
+            if num in disallowed_set:
+                is_valid = False
+                break
+            for cannot_come_before in reversed_graph[num]:
+                if not cannot_come_before in seen_set:
+                    disallowed_set.add(cannot_come_before)
+
+            seen_set.add(num)
+
+        if is_valid:
+            part1_ans += update[len(update) // 2]
+        else:
+            invalid_updates.append(update)
+    if part == 1:
+        return part1_ans
+
+    # part2
+    # can assume there's only one valid order... or that unordered ones will not affect the middle value
+    # so just take all the numbers and create the correct order by traversing the graph of dependencies?
+
+    part2_ans: int = 0
+    for update in invalid_updates:
+        correct_order: list[int] = []
+        all_nums: set[int] = set(update)
+        used_nums: set[int] = set()
+        while len(all_nums) > len(used_nums):
+            for num in all_nums:
+                if num in used_nums:
+                    continue
+                if not num in reversed_graph:
+                    correct_order.append(num)
+                    # all_nums.remove(num)
+                    used_nums.add(num)
+                    continue
+
+                # check if all of this num's dependencies are in used_nums
+                # or if its dependencies are not present at all
+                # there's definitely a better algo for this...
+                if all(
+                    [
+                        dep in used_nums or not dep in all_nums
+                        for dep in reversed_graph[num]
+                    ]
+                ):
+                    correct_order.append(num)
+                    # all_nums.remove(num)
+                    used_nums.add(num)
+                    continue
+        part2_ans += correct_order[len(correct_order) // 2]
+
+    return part2_ans
+
+
+# page ordering rules, X|Y -> X must come before Y
+# updates, basically orders of pages
+#   missing page numbers are ignored..
+# part1_ans: sum middle page of each valid update
+example = """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"""
+
+input = open("input.txt").read()
+
+print(f"day5 example: {day5(example,1)} want 143")
+print(f"day5: {day5(input,1)} want 5166")
+
+print(f"part2 example: {day5(example,2)} want 123")
+print(f"part2: {day5(input,2)} want 4679")