From 6f8168631f79f99b8097d400b7ac6fe4cb3b0a68 Mon Sep 17 00:00:00 2001
From: Allianzcortex <iamwanghz@gmail.com>
Date: Sat, 7 Dec 2024 09:56:16 -0500
Subject: [PATCH] add day7 solution

---
 advent_of_code/2024(python)/day7.py      | 60 ++++++++++++++++++++++++
 advent_of_code/2024(python)/test_day7.py | 27 +++++++++++
 2 files changed, 87 insertions(+)
 create mode 100644 advent_of_code/2024(python)/day7.py
 create mode 100644 advent_of_code/2024(python)/test_day7.py

diff --git a/advent_of_code/2024(python)/day7.py b/advent_of_code/2024(python)/day7.py
new file mode 100644
index 0000000..daa7333
--- /dev/null
+++ b/advent_of_code/2024(python)/day7.py
@@ -0,0 +1,60 @@
+
+
+def _is_equal_part1(target:int, nums:list[int], prefix:int)->bool:
+    if (not nums):
+        return prefix == target
+    
+    is_equal = False
+    
+    # we can do `*` or `+` 2 operators
+    prefix_mul = prefix*nums[0]
+    is_equal = is_equal or _is_equal_part1(target,nums[1:],prefix_mul)
+
+    prefix_add = prefix+nums[0]
+    is_equal = is_equal or _is_equal_part1(target,nums[1:],prefix_add)
+
+    return is_equal
+
+
+def solve_day7_part1(matrix:list[str])->int:
+    res = 0
+    for line in matrix:
+        expected_answer, given_input = line.split(":")
+        target = int(expected_answer)
+        nums = [int(num) for num in given_input.strip().split(" ")]
+        if _is_equal_part1(target, nums[1:],nums[0]):
+            res += target
+    
+    return res
+
+
+
+def _is_equal_part2(target:int, nums:list[int], prefix:int)->bool:
+    if (not nums):
+        return prefix == target
+    
+    is_equal = False
+    
+    # we can do `*` or `+` or `||` 3 operators
+    prefix_mul = prefix*nums[0]
+    is_equal = is_equal or _is_equal_part2(target,nums[1:],prefix_mul)
+
+    prefix_add = prefix+nums[0]
+    is_equal = is_equal or _is_equal_part2(target,nums[1:],prefix_add)
+
+    prefix_concat = int(str(prefix) + str(nums[0]))
+    is_equal = is_equal or _is_equal_part2(target,nums[1:],prefix_concat)
+
+    return is_equal
+
+
+def solve_day7_part2(matrix:list[str])->int:
+    res = 0
+    for line in matrix:
+        expected_answer, given_input = line.split(":")
+        target = int(expected_answer)
+        nums = [int(num) for num in given_input.strip().split(" ")]
+        if _is_equal_part2(target, nums[1:],nums[0]):
+            res += target
+
+    return res
\ No newline at end of file
diff --git a/advent_of_code/2024(python)/test_day7.py b/advent_of_code/2024(python)/test_day7.py
new file mode 100644
index 0000000..721d640
--- /dev/null
+++ b/advent_of_code/2024(python)/test_day7.py
@@ -0,0 +1,27 @@
+import unittest
+
+from day7 import solve_day7_part1, solve_day7_part2
+
+
+input7 = [
+"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",
+]
+
+class TestDay7(unittest.TestCase):
+
+    def test_part1(self):
+        self.assertEqual(solve_day7_part1(input7), 3749)
+
+    def test_part2(self):
+        self.assertEqual(solve_day7_part2(input7), 11387)
+
+if __name__ == "__main__":
+    unittest.main()