🎉D4P2 Complete!

aoc_25/solutions/day04.py

@@ -4,6 +4,7 @@
 from utils.aoc_utils import report_results, AoCResult, input_for_day
 
 LooRollGrid = list[list[str]]
+RollCoord = tuple[int, int]
 
 ORIGINAL_EXAMPLE: str = """..@@.@@@@.
 @@@.@.@.@@
@@ -21,30 +22,22 @@
 DATA: LooRollGrid = [list(x) for x in INPUT_DATA]
 
 
-def parse_loogrid_p1(data: LooRollGrid) -> int:
-    """Navigate through the Loo Roll Grid for AOCD4P1.
-
-    Insert an extra layer of blank padding, slide a
-    3x3 window and count adjacent loo rolls.
-    If less than 4 adjacent loo rolls, count it!
+def forklift(data: LooRollGrid) -> list[RollCoord]:
+    """Forklift operations. Go through grid, find '@',
+    get window and check adjacent '@'.
+    If valid - add to list of valid coordinates.
 
     Args:
-        data (LooRollGrid): List of lists, @ = loo roll.
+        data (LooRollGrid): Puzzle input as a list of lists.
 
     Returns:
-        int: Count of valid positions.
+        list[RollCoord]: list of valid coordinates.
     """
-    forklift_access: int = 0
-    # add an extra padding 0 and -1
-    for row in data:
-        row.insert(0, ".")
-        row.insert(len(data[0]), ".")
-
-    # add an extra layer of padding...
-    data.insert(0, list("." * len(data[0])))
-    data.insert(len(data), list("." * len(data[0])))
-
     # trundle through the grid
+    coords: list[RollCoord] = []
+    row_idx: int
+    col_idx: int
+
     for row_idx, row in enumerate(data[1:-1], 1):
         # print(ri, row[1:-1])
         for col_idx, col in enumerate(row[1:-1], 1):
@@ -59,18 +52,81 @@ def parse_loogrid_p1(data: LooRollGrid) -> int:
                 # deduct the initial @
                 num_rolls: int = join_window.count("@") - 1
                 if num_rolls < 4:
-                    forklift_access += 1
-    return forklift_access
+                    coords.append((row_idx, col_idx))
+
+    return coords
+
+
+def pad_data(data: LooRollGrid) -> LooRollGrid:
+    """Pad initial grid with blanks.
+
+    Args:
+        data (LooRollGrid): Puzzle input grid.
+
+    Returns:
+        LooRollGrid: Padded puzzle grid.
+    """
+    # add an extra padding 0 and -1
+    padded_data: LooRollGrid = data.copy()
+    for row in padded_data:
+        row.insert(0, ".")
+        row.insert(len(data[0]), ".")
+
+    # add an extra layer of padding...
+    padded_data.insert(0, list("." * len(padded_data[0])))
+    padded_data.insert(len(padded_data), list("." * len(padded_data[0])))
+
+    return padded_data
+
+
+def solve_p1(data: LooRollGrid) -> int:
+    """Solve P1. Iterate once - find valid coords.
+
+    Args:
+        data (LooRollGrid): Puzzle input.
+
+    Returns:
+        int: Number of valid loo roll coords.
+    """
+    padded_data = pad_data(data)
+    valid_rolls = forklift(padded_data)
+    return len(valid_rolls)
+
+
+def solve_p2(data: LooRollGrid) -> int:
+    """Recursively search for valid coords,
+    add to coordinate list. Replace those coords with 'x',
+    then repeat until no more can be replaced.
+
+    Args:
+        data (LooRollGrid): Puzzle input.
+
+    Returns:
+        int: Total valid loo roll removals.
+    """
+    padded_data: LooRollGrid = pad_data(data)
+    total_removed: int = 0
+
+    while True:
+        coords: list[RollCoord] = forklift(padded_data)
+        if not coords:
+            break
+
+        for x in coords:
+            padded_data[x[0]][x[1]] = 'x'
+        total_removed += len(coords)
+
+    return total_removed
 
 
 @report_results
 def solveday(data: Any) -> AoCResult:
-    p1: int = parse_loogrid_p1(data)
-    p2: int = 0
+    p1: int = solve_p1([row.copy() for row in data])
+    p2: int = solve_p2([row.copy() for row in data])
     return p1, p2
 
 
-expected_test_results: AoCResult = (13, 0)
+expected_test_results: AoCResult = (13, 43)
 
 
 def tests(test_input: Any) -> None: