Day 3 (Puzzle 2) - Rucksack Reorganization

Successfully finished the second puzzle.
Took me a bit worrying what "and at most two of the Elves will be carrying any other item type" meant in the task text while my grouping loop was broken and skipping a rucksack every fourth rucksack while doing the group. Yikes.

Caught the error before trying a result though thanks to exceptions when things go wrong!

entities/elf.py

@@ -76,13 +76,33 @@ class Elf:
 
         return was_win, round_score + RPS.RPS_SHAPE_TO_SCORE[own]
 
-    def check_rucksack_for_compartment_duplicates(self, rucksack: Tuple[List[str], List[str]]) -> str:
+    @staticmethod
+    def check_rucksacks_for_duplicates(rucksack1: Tuple[List[str], List[str]], rucksack2: Tuple[List[str], List[str]]) -> List[str]:
         """
-        Check a given rucksack for the duplicate item according to day 3 puzzle 1
-        :return: the duplicate item (as a character)
+        Check if rucksack1 and rucksack2 have an item in common. This will merge the compartments in each rucksack.
+
+        :param rucksack1:
+        :param rucksack2:
+        :return: list of the duplicate item (as a character) or None if there is no duplicate
         """
-        for a in rucksack[0]:
-            if a in rucksack[1]:
+        r1 = list(set(rucksack1[0] + rucksack1[1]))
+        r2 = list(set(rucksack2[0] + rucksack2[1]))
+
+        dups = []
+        for a in r1:
+            if a in r2:
+                dups.append(a)
+
+        return dups
+
+    @staticmethod
+    def check_compartments_for_duplicates(compartment_1: List[str], compartment_2: List[str]) -> str:
+        """
+        Check two given compartment for the duplicate item according to day 3 puzzle 1
+        :return: the duplicate item (as a character) or None if there is no duplicate
+        """
+        for a in compartment_1:
+            if a in compartment_2:
                 return a
 
-        raise ValueError(f"Couldn't find ANY duplicate in this rucksack: {rucksack[0]} | {rucksack[1]}")
+        return False

main.py

@@ -6,12 +6,33 @@ from entities.elf import Elf
 if __name__ == "__main__":
     rs = RucksackLoader("./input/day3/input.lst").parse_file()
     i = item_priority
-    duplicate_prios = []
-    for rucksack in rs:
-        elf = Elf()
-        duplicate = elf.check_rucksack_for_compartment_duplicates(rucksack)
-        duplicate_prios.append(item_priority[duplicate])
-        print(f"{elf} found duplicate \"{duplicate}\" with priority {item_priority[duplicate]}!")
 
-    print()
-    print(f"The priority sum is {sum(duplicate_prios)}")
+    groups = []
+    curr_group = []
+    for rucksack in rs:  # creating groups of 3
+        elf = Elf()
+        curr_group.append((elf, rucksack))
+        if len(curr_group) >= 3:
+            groups.append(curr_group)
+            curr_group = []
+
+    group_badges = []
+    for i in range(len(groups)):
+        group = groups[i]
+        dup1 = Elf.check_rucksacks_for_duplicates(group[0][1], group[1][1])
+        dup2 = Elf.check_rucksacks_for_duplicates(group[0][1], group[2][1])
+
+        r = Elf.check_compartments_for_duplicates(dup1, dup2)
+        if r:
+            final_dup = r
+            print(f"Group #{i} has the badge item {final_dup} ({item_priority[final_dup]})")
+        else:
+            final_dup = None
+            raise ValueError(f"Found no badge item for Group #{i}")
+
+        group_badges.append(final_dup)
+
+    print("")
+    print(f"The priority sum is: {sum([item_priority[c] for c in group_badges])}")
+
+