i do not love this code

2024/day08/day08.py

@@ -0,0 +1,120 @@
+from collections import defaultdict
+
+
+def part1(input: str) -> int:
+    grid = [list(line) for line in input.splitlines()]
+    map_antenna_to_coords: dict[str, list[tuple[int, int]]] = defaultdict(list)
+    for i in range(len(grid)):
+        for j in range(len(grid[0])):
+            if grid[i][j] != ".":
+                map_antenna_to_coords[grid[i][j]].append((i, j))
+
+    rows = len(grid)
+    cols = len(grid[0])
+
+    anti_node_coords: set[tuple[int, int]] = set()
+
+    for _, coords in map_antenna_to_coords.items():
+
+        for i in range(len(coords)):
+            c1 = coords[i]
+            for j in range(i + 1, len(coords)):
+                c2 = coords[j]
+
+                if c1 == c2:
+                    continue
+
+                rowDiff: int = c2[0] - c1[0]
+                colDiff: int = c2[1] - c1[1]
+
+                maybeRow: int = c1[0] - rowDiff
+                maybeCol: int = c1[1] - colDiff
+                if (
+                    0 <= maybeRow < rows
+                    and 0 <= maybeCol < cols
+                    and (maybeRow, maybeCol) != c1
+                    and (maybeRow, maybeCol) != c2
+                ):
+                    anti_node_coords.add((maybeRow, maybeCol))
+
+                maybeRow: int = c2[0] + rowDiff
+                maybeCol: int = c2[1] + colDiff
+                if (
+                    0 <= maybeRow < rows
+                    and 0 <= maybeCol < cols
+                    and (maybeRow, maybeCol) != c1
+                    and (maybeRow, maybeCol) != c2
+                ):
+                    anti_node_coords.add((maybeRow, maybeCol))
+
+    return len(anti_node_coords)
+
+
+def part2(input: str) -> int:
+    grid = [list(line) for line in input.splitlines()]
+    map_antenna_to_coords: dict[str, list[tuple[int, int]]] = defaultdict(list)
+    for i in range(len(grid)):
+        for j in range(len(grid[0])):
+            if grid[i][j] != ".":
+                map_antenna_to_coords[grid[i][j]].append((i, j))
+
+    rows = len(grid)
+    cols = len(grid[0])
+
+    anti_node_coords: set[tuple[int, int]] = set()
+
+    for _, coords in map_antenna_to_coords.items():
+
+        for i in range(len(coords)):
+            c1 = coords[i]
+
+            # a more elegant solution would be to calculate the starting point of the antenna's line
+            # then do a single loop to find all anti-node coords
+            # instead, i'll just go left and right from c1, and add c1 manually
+            anti_node_coords.add(c1)
+
+            for j in range(i + 1, len(coords)):
+                c2 = coords[j]
+
+                if c1 == c2:
+                    continue
+
+                rowDiff: int = c2[0] - c1[0]
+                colDiff: int = c2[1] - c1[1]
+
+                maybeRow: int = c1[0] - rowDiff
+                maybeCol: int = c1[1] - colDiff
+                while 0 <= maybeRow < rows and 0 <= maybeCol < cols:
+                    anti_node_coords.add((maybeRow, maybeCol))
+                    maybeRow -= rowDiff
+                    maybeCol -= colDiff
+
+                maybeRow: int = c1[0] + rowDiff
+                maybeCol: int = c1[1] + colDiff
+                while 0 <= maybeRow < rows and 0 <= maybeCol < cols:
+                    anti_node_coords.add((maybeRow, maybeCol))
+                    maybeRow += rowDiff
+                    maybeCol += colDiff
+
+    return len(anti_node_coords)
+
+
+example = """............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............"""
+
+input = open("input.txt").read()
+
+print(f"part1 example: {part1(example)} want 14")
+print(f"part1: {part1(input)} want 396")
+print(f"part2 example: {part2(example)} want 34")
+print(f"part2: {part2(input)} want 1200")