From c871a9ea245d490305052ee49429726abc503b7d Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Sat, 7 Dec 2024 10:35:58 +0100
Subject: [PATCH] Implement 2024 day 7

---
 2024/src/aoc/days/day7.py | 61 +++++++++++++++++++++++++++++++++++++++
 2024/tests/samples/07.txt |  9 ++++++
 2024/tests/test_day07.py  | 17 +++++++++++
 3 files changed, 87 insertions(+)
 create mode 100644 2024/src/aoc/days/day7.py
 create mode 100644 2024/tests/samples/07.txt
 create mode 100644 2024/tests/test_day07.py

diff --git a/2024/src/aoc/days/day7.py b/2024/src/aoc/days/day7.py
new file mode 100644
index 0000000..67ac735
--- /dev/null
+++ b/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])
+        )
diff --git a/2024/tests/samples/07.txt b/2024/tests/samples/07.txt
new file mode 100644
index 0000000..fc6e099
--- /dev/null
+++ b/2024/tests/samples/07.txt
@@ -0,0 +1,9 @@
+190: 10 19
+3267: 81 40 27
+83: 17 5
+156: 15 6
+7290: 6 8 6 15
+161011: 16 10 13
+192: 17 8 14
+21037: 9 7 18 13
+292: 11 6 16 20
diff --git a/2024/tests/test_day07.py b/2024/tests/test_day07.py
new file mode 100644
index 0000000..b80ba94
--- /dev/null
+++ b/2024/tests/test_day07.py
@@ -0,0 +1,17 @@
+import os
+
+from aoc.days.day7 import DayRunner
+
+
+def get_data() -> str:
+    sample = os.path.dirname(__file__) + "/samples/07.txt"
+    with open(sample, mode="rt", encoding="utf-8") as f:
+        return f.read()
+
+
+def test_sample_part1() -> None:
+    assert DayRunner.part1(get_data()) == 3749
+
+
+def test_sample_part2() -> None:
+    assert DayRunner.part2(get_data()) == 11387