Advent of Code 2025 - Day 2 : Python version

advent_of_code/2025(python)/day2.py

@@ -0,0 +1,61 @@
+def solve_day2_part1_wrong_version(input_):
+    # only work for test case
+    res = 0
+    for ranges in input_.split(","):
+        left, right = ranges.split("-")
+
+        invalid_left = invalid_right = ""
+        if len(left) % 2 == 0:
+            left_left_half = left[:len(left)//2]
+            left_right_half = left[len(left)//2:]
+            if int(left_left_half) >= int(left_right_half):
+                invalid_left = left_left_half+left_left_half
+
+        if len(right) % 2 == 0:
+            right_left_half = right[:len(right)//2]
+            right_right_half = right[len(right)//2:]
+            if int(right_left_half) <= int(right_right_half) and int(right_left_half) >= int(left_right_half):
+                invalid_right = right_left_half + right_left_half
+            if int(left_left_half) > int(right_right_half):
+                invalid_left = ""
+
+        res += int(invalid_left) if invalid_left != "" else 0
+        res += int(invalid_right) if invalid_right != "" and invalid_left != invalid_right else 0
+
+    return res
+
+
+def solve_day2_part1_right_version(input_):
+    res = 0
+    for ranges in input_.split(","):
+        left, right = ranges.split("-")
+        # both are odds
+        if len(left) % 2 == 1 and len(right) % 2 == 1:
+            continue
+
+        left_val, right_val = int(left), int(right)
+        # if left is even
+        if len(left) % 2 == 0:
+            left_left_half = int(left[:len(left)//2])
+            while True:
+                next_val = f"{left_left_half}{left_left_half}"
+                if left_val <= int(next_val) <= right_val:
+                    res += int(next_val)
+                elif int(next_val) > right_val:
+                    break
+
+                left_left_half += 1
+
+        # if right is even
+        elif len(right) % 2 == 0:
+            right_left_half = int(right[:len(right)//2])
+            while True:
+                next_val = f"{right_left_half}{right_left_half}"
+                if left_val <= int(next_val) <= right_val:
+                    res += int(next_val)
+                elif int(next_val) < left_val:
+                    break
+
+                right_left_half -= 1
+
+    return res

advent_of_code/2025(python)/test_day2.py

@@ -0,0 +1,17 @@
+import unittest
+
+from day2 import solve_day2_part1_right_version
+
+question_input = "11-22,95-115,998-1012,1188511880-1188511890,222220-222224,\
+1698522-1698528,446443-446449,38593856-38593862,565653-565659,\
+824824821-824824827,2121212118-2121212124"
+
+
+class TestSample(unittest.TestCase):
+    def test_part1(self):
+        self.assertEqual(solve_day2_part1_right_version(
+            question_input), 1227775554)
+
+
+if __name__ == "__main__":
+    unittest.main()