Advent of Code 2024 - Day 2 : Python version

advent_of_code/2024(python)/day2.py

@@ -0,0 +1,80 @@
+
+def _is_single_record_safe(record:list[int]) -> bool:
+
+    if not 1 <= abs(record[0] - record[1]) <= 3:
+        return False
+    is_increasing = record[0] < record[1]
+
+    for i in range(1, len(record)-1):
+        diff = record[i] - record[i+1]
+        if (is_increasing and diff>0) or (not is_increasing and diff<0):
+            return False
+        if not 1 <= abs(diff) <= 3:
+            return False
+
+    return True
+
+def _is_single_record_wrong_version(record:list[int]) -> bool:
+    if not 1 <= abs(record[0] - record[1]) <= 3:
+        # so we can remove either first or second
+        remove_1st_item_record = record[1:]
+        remove_2nd_item_record = record[:1] + record[2:]
+        return _is_single_record_safe(remove_1st_item_record) or _is_single_record_safe(remove_2nd_item_record)
+
+    is_increasing = record[0] < record[1]
+
+    for i in range(1, len(record)-1):
+        diff = record[i] - record[i+1]
+        if (is_increasing and diff>0) or (not is_increasing and diff<0) or (not 1 <= abs(diff) <= 3):
+            # either remove ith or (i+1)th item
+            remove_ith_item_record = record[:i] + record[i+1:]
+            remove_i1th_item_record = record[:i+1] + record[i+2:]
+            return _is_single_record_safe(remove_ith_item_record) or _is_single_record_safe(remove_i1th_item_record)
+
+    return True
+
+def _is_single_record_safe_right_version(record:list[int]) -> bool:
+    if not 1 <= abs(record[0] - record[1]) <= 3:
+        # so we can remove either first or second
+        remove_1st_item_record = record[1:]
+        remove_2nd_item_record = record[:1] + record[2:]
+        return _is_single_record_safe(remove_1st_item_record) or _is_single_record_safe(remove_2nd_item_record)
+
+    is_increasing = record[0] < record[1]
+
+    for i in range(1, len(record)-1):
+        diff = record[i] - record[i+1]
+        if (is_increasing and diff>0) or (not is_increasing and diff<0) or (not 1 <= abs(diff) <= 3):
+            # try brutefocelly iterating all items
+            is_safe = False
+            for i in range(len(record)):
+                is_safe = is_safe or _is_single_record_safe(record[:i] + record[i+1:])
+
+            return is_safe
+
+    return True
+
+
+def solve_day2_part1(inp:list[str]) -> int:
+
+    res = 0
+    for report in inp:
+        record = [int(item) for item in report.split()]
+
+        res += int(_is_single_record_safe(record))
+
+    return res
+
+def solve_day2_part2(inp:list[str]) -> int:
+
+    res = 0
+    for report in inp:
+        record = [int(item) for item in report.split()]
+        # Uses `_is_single_record_wrong_version` previously
+        # Get answer 530, while expected answer is 531
+        # Wrong version can't solve `65 66 63 60`
+        # it will be valid when removing first item : 66 63 60
+        # but previous version will only try : 65 66 60 and 66 63 60
+        res += int(_is_single_record_safe_right_version(record))
+
+    return res

advent_of_code/2024(python)/test_day2.py

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+import unittest
+
+from day2 import solve_day2_part1, solve_day2_part2
+
+question2_input = [
+"7 6 4 2 1",
+"1 2 7 8 9",
+"9 7 6 2 1",
+"1 3 2 4 5",
+"8 6 4 4 1",
+"1 3 6 7 9",
+]
+
+
+class TestDay2(unittest.TestCase):
+
+    def test_part1(self):
+        self.assertEqual(solve_day2_part1(question2_input), 2)
+
+    def test_part2(self):
+        self.assertEqual(solve_day2_part2(question2_input), 4)
+
+if __name__ == "__main__":
+    unittest.main()