Implement 2024 day 7

2024/src/aoc/days/day7.py

@@ -0,0 +1,61 @@
+from . import SeparateRunner
+
+
+def parse_input(input: str) -> tuple[int, list[int]]:
+    result = []
+
+    for line in input.strip().split("\n"):
+        test, nums = line.split(": ")
+        result.append((int(test), list(map(int, nums.split(" ")))))
+
+    return result
+
+
+def is_possible(target: int, nums: list[int], cur: int) -> bool:
+    if cur == target and not nums:
+        return True
+
+    if cur > target or not nums:
+        return False
+
+    head = nums[0]
+    remainder = nums[1:]
+
+    return is_possible(target, remainder, cur + head) or is_possible(
+        target, remainder, cur * head
+    )
+
+
+def is_possible2(target: int, nums: list[int], cur: int) -> bool:
+    if cur == target and not nums:
+        return True
+
+    if cur > target or not nums:
+        return False
+
+    head = nums[0]
+    remainder = nums[1:]
+
+    return (
+        is_possible2(target, remainder, cur + head)
+        or is_possible2(target, remainder, cur * head)
+        or is_possible2(target, remainder, int(f"{cur}{head}"))
+    )
+
+
+class DayRunner(SeparateRunner):
+    @classmethod
+    def part1(cls, input: str) -> int:
+        lines = parse_input(input)
+
+        return sum(
+            target for target, nums in lines if is_possible(target, nums[1:], nums[0])
+        )
+
+    @classmethod
+    def part2(cls, input: str) -> int:
+        lines = parse_input(input)
+
+        return sum(
+            target for target, nums in lines if is_possible2(target, nums[1:], nums[0])
+        )