Use Counter container type

Replace uses of custom dict in cases where Counter container type is
applicable.

adventofcode/d4.py

@@ -1,3 +1,4 @@
+from collections import Counter
 from dataclasses import dataclass
 from typing import Iterable
 
@@ -35,11 +36,15 @@ def p1(input_: str) -> int:
 def p2(input_str: str) -> int:
     d = list(_parse_input(input_str.splitlines()))
 
-    counts: dict[int, int] = {n + 1: 1 for n in range(len(d))}
+    counts: Counter[int] = Counter(range(1, len(d) + 1))
     for cards in d:
         matches = len(set(cards.winning) & set(cards.own))
         card_count = counts[cards.card_id]
-        for i in range(cards.card_id + 1, cards.card_id + 1 + matches):
-            counts[i] += card_count
+        counts.update(
+            {
+                i: card_count
+                for i in range(cards.card_id + 1, cards.card_id + 1 + matches)
+            }
+        )
 
     return sum(v for v in counts.values())

adventofcode/d7.py

@@ -1,4 +1,5 @@
 import enum
+from collections import Counter
 from dataclasses import dataclass
 from functools import total_ordering
 from types import NotImplementedType
@@ -48,21 +49,19 @@ def p1(input_str: str) -> int:
 
     def classify_hand_type(cards: str) -> HandType:
         assert len(cards) == 5
-        value_counts: dict[str, int] = {}
-        for c in cards:
-            value_counts[c] = value_counts.get(c, 0) + 1
+        value_counts = Counter[str](cards)
+        counts = list(map(lambda x: x[1], value_counts.most_common(2)))
 
-        counts = sorted(value_counts.items(), key=lambda x: x[1], reverse=True)
-        if counts[0][1] == 5:
+        if counts[0] == 5:
             return HandType.FiveOfAKind
-        if counts[0][1] == 4:
+        if counts[0] == 4:
             return HandType.FourOfAKind
-        if counts[0][1] == 3:
-            if counts[1][1] == 2:
+        if counts[0] == 3:
+            if counts[1] == 2:
                 return HandType.FullHouse
             return HandType.ThreeOfAKind
-        if counts[0][1] == 2:
-            if counts[1][1] == 2:
+        if counts[0] == 2:
+            if counts[1] == 2:
                 return HandType.TwoPair
             return HandType.OnePair
         return HandType.HighCard
@@ -95,27 +94,25 @@ def p2(input_str: str) -> int:
 
     def classify_hand_type(cards: str) -> HandType:
         assert len(cards) == 5
-        value_counts: dict[str, int] = {}
-        for c in cards:
-            value_counts[c] = value_counts.get(c, 0) + 1
+        value_counts = Counter[str](cards)
 
         jokers = value_counts.get("J", 0)
         value_counts.pop("J", None)
 
         if jokers == 5:
             return HandType.FiveOfAKind
 
-        counts = sorted(value_counts.items(), key=lambda x: x[1], reverse=True)
-        if counts[0][1] + jokers == 5:
+        counts = list(map(lambda x: x[1], value_counts.most_common(2)))
+        if counts[0] + jokers == 5:
             return HandType.FiveOfAKind
-        if counts[0][1] + jokers == 4:
+        if counts[0] + jokers == 4:
             return HandType.FourOfAKind
-        if counts[0][1] + jokers == 3:
-            if counts[1][1] == 2:
+        if counts[0] + jokers == 3:
+            if counts[1] == 2:
                 return HandType.FullHouse
             return HandType.ThreeOfAKind
-        if counts[0][1] + jokers == 2:
-            if counts[1][1] == 2:
+        if counts[0] + jokers == 2:
+            if counts[1] == 2:
                 return HandType.TwoPair
             return HandType.OnePair
         return HandType.HighCard