solve Day13 with Python

Day13/README.md

@@ -65,4 +65,64 @@ This pattern reflects across the horizontal line between rows 4 and 5. Row 1 wou
 
 To summarize your pattern notes, add up the number of columns to the left of each vertical line of reflection; to that, also add 100 multiplied by the number of rows above each horizontal line of reflection. In the above example, the first pattern's vertical line has 5 columns to its left and the second pattern's horizontal line has 4 rows above it, a total of 405.
 
-Find the line of reflection in each of the patterns in your notes. What number do you get after summarizing all of your notes?
+Find the line of reflection in each of the patterns in your notes. What number do you get after summarizing all of your notes?
+
+## Part Two 
+You resume walking through the valley of mirrors and - SMACK! - run directly into one. Hopefully nobody was watching, because that must have been pretty embarrassing.
+
+Upon closer inspection, you discover that every mirror has exactly one smudge: exactly one . or # should be the opposite type.
+
+In each pattern, you'll need to locate and fix the smudge that causes a different reflection line to be valid. (The old reflection line won't necessarily continue being valid after the smudge is fixed.)
+
+Here's the above example again:
+```
+#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.
+```
+
+```
+#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#
+```
+
+The first pattern's smudge is in the top-left corner. If the top-left # were instead ., it would have a different, horizontal line of reflection:
+
+```
+1 ..##..##. 1
+2 ..#.##.#. 2
+3v##......#v3
+4^##......#^4
+5 ..#.##.#. 5
+6 ..##..##. 6
+7 #.#.##.#. 7
+```
+
+With the smudge in the top-left corner repaired, a new horizontal line of reflection between rows 3 and 4 now exists. Row 7 has no corresponding reflected row and can be ignored, but every other row matches exactly: row 1 matches row 6, row 2 matches row 5, and row 3 matches row 4.
+
+In the second pattern, the smudge can be fixed by changing the fifth symbol on row 2 from . to #:
+
+```
+1v#...##..#v1
+2^#...##..#^2
+3 ..##..### 3
+4 #####.##. 4
+5 #####.##. 5
+6 ..##..### 6
+7 #....#..# 7
+```
+
+Now, the pattern has a different horizontal line of reflection between rows 1 and 2.
+
+Summarize your notes as before, but instead use the new different reflection lines. In this example, the first pattern's new horizontal line has 3 rows above it and the second pattern's new horizontal line has 1 row above it, summarizing to the value 400.
+
+In each pattern, fix the smudge and find the different line of reflection. What number do you get after summarizing the new reflection line in each pattern in your notes?

Day13/python/solution2.py

@@ -0,0 +1,67 @@
+from itertools import groupby
+
+def find_mirror(group):
+    """
+    Find the line of symmetry in the pattern, considering there may be one smudge.
+    Returns the position of the line of symmetry or 0 if none found.
+    """
+    for i in range(1, len(group)):
+        above = group[:i][::-1]
+        below = group[i:]
+        if sum(sum(a != b for a, b in zip(x, y)) for x, y in zip(above, below)) == 1:
+            return i
+    return 0
+
+def process_file(filename):
+    """
+    Process the given file to find the sum of mirror lines considering smudges.
+    """
+    try:
+        with open(filename) as f:
+            lines = f.read().splitlines()
+
+        groups = [tuple(group) for not_empty, group in groupby(lines, bool) if not_empty]
+
+        res = 0
+        for group in groups:
+            # Vertical reflection
+            res += find_mirror(group) * 100
+            # Horizontal reflection
+            res += find_mirror(tuple(zip(*group)))
+        
+        return res
+
+    except Exception as e:
+        print(f"Error processing file {filename}: {e}")
+        raise
+
+def test():
+    """
+    Test function to verify the algorithm with test data.
+    """
+    try:
+        test_result = process_file("../test.txt")
+        print(f"Test result: {test_result}")
+        expected_result = 400  # Adjust this based on the expected outcome of the test data
+        assert test_result == expected_result, f"Test failed. Expected result is {expected_result}."
+        print("Test passed.")
+    except AssertionError as ae:
+        print(ae)
+    except Exception as e:
+        print(f"Test error: {e}")
+
+def main():
+    """
+    Main function to process the actual input file.
+    """
+    print("Starting tests...")
+    test()
+    
+    try:
+        final_result = process_file("../input.txt")
+        print(f"Final result: {final_result}")
+    except Exception as e:
+        print(f"An error occurred: {e}")
+
+if __name__ == "__main__":
+    main()