Day 10

aoc_cas/aoc2023/day10.py

@@ -0,0 +1,111 @@
+def create_graph(data: str) -> tuple[tuple[int, int], list[list[int]]]:
+    lines = data.splitlines()
+    M, N = len(lines), len(lines[0])
+
+    edges = [[1] * (2 * N + 1) for _ in range(2 * M + 1)]
+    start = -1, -1
+    for y, row in enumerate(lines):
+        yy = y * 2 + 1
+        for x, v in enumerate(row):
+            xx = x * 2 + 1
+            edges[yy - 1][xx - 1] = 0
+            edges[yy - 1][xx + 1] = 0
+            edges[yy + 1][xx - 1] = 0
+            edges[yy + 1][xx + 1] = 0
+            match v:
+                case "|":
+                    edges[yy - 1][xx] &= 1
+                    edges[yy + 1][xx] &= 1
+                    edges[yy][xx - 1] &= 0
+                    edges[yy][xx + 1] &= 0
+                case "-":
+                    edges[yy - 1][xx] &= 0
+                    edges[yy + 1][xx] &= 0
+                    edges[yy][xx - 1] &= 1
+                    edges[yy][xx + 1] &= 1
+                case "L":
+                    edges[yy - 1][xx] &= 1
+                    edges[yy + 1][xx] &= 0
+                    edges[yy][xx - 1] &= 0
+                    edges[yy][xx + 1] &= 1
+                case "J":
+                    edges[yy - 1][xx] &= 1
+                    edges[yy + 1][xx] &= 0
+                    edges[yy][xx - 1] &= 1
+                    edges[yy][xx + 1] &= 0
+                case "7":
+                    edges[yy - 1][xx] &= 0
+                    edges[yy + 1][xx] &= 1
+                    edges[yy][xx - 1] &= 1
+                    edges[yy][xx + 1] &= 0
+                case "F":
+                    edges[yy - 1][xx] &= 0
+                    edges[yy + 1][xx] &= 1
+                    edges[yy][xx - 1] &= 0
+                    edges[yy][xx + 1] &= 1
+                case ".":
+                    edges[yy][xx] = 0
+                    edges[yy - 1][xx] &= 0
+                    edges[yy + 1][xx] &= 0
+                    edges[yy][xx - 1] &= 0
+                    edges[yy][xx + 1] &= 0
+                case "S":
+                    edges[yy - 1][xx] &= 1
+                    edges[yy + 1][xx] &= 1
+                    edges[yy][xx - 1] &= 1
+                    edges[yy][xx + 1] &= 1
+                    start = yy, xx
+                case _:
+                    edges[yy][xx] = 0
+                    edges[yy - 1][xx] &= 0
+                    edges[yy + 1][xx] &= 0
+                    edges[yy][xx - 1] &= 0
+                    edges[yy][xx + 1] &= 0
+    return start, edges
+
+
+def trace_path(start: tuple[int, int], graph: list[list[int]]) -> list[tuple[int, int]]:
+    current = start
+    path = []
+    prev = None
+    while not (prev == start and len(path) > 2):
+        y, x = current
+        for dy, dx in ((-1, 0), (1, 0), (0, -1), (0, 1)):
+            if graph[y + dy][x + dx] == 1 and graph[y + 2 * dy][x + 2 * dx] == 1 and (y + 2 * dy, x + 2 * dx) != prev:
+                prev = current
+                path.append((y + dy, x + dx))
+                path.append((y + 2 * dy, x + 2 * dx))
+                current = y + 2 * dy, x + 2 * dx
+                break
+    return path[:-1]
+
+
+def part_a(data: str) -> int:
+    start, graph = create_graph(data)
+    path = trace_path(start, graph)
+    return len(path) // 4
+
+
+def part_b(data: str) -> int:
+    start, graph = create_graph(data)
+    path = trace_path(start, graph)
+    M, N = len(graph), len(graph[0])
+    current = {(0, 0)}  # Guaranteed to not be part of path
+    seen = set(path)
+    while current:
+        nxt = set()
+        for y, x in current - seen:
+            seen.add((y, x))
+            for dy, dx in ((-1, 0), (1, 0), (0, -1), (0, 1)):
+                if 0 <= y + dy < M and 0 <= x + dx < N:
+                    nxt.add((y + dy, x + dx))
+        current = nxt
+
+    all_nodes = {(y, x) for y in range(M) for x in range(N) if y % 2 == 1 and x % 2 == 1}
+    return len(all_nodes - seen)
+
+
+if __name__ == "__main__":
+    from aoc_cas.util import solve_with_examples
+
+    solve_with_examples(year=2023, day=10)

tests/fixtures/2023/10.txt

@@ -0,0 +1,65 @@
+.....
+.S-7.
+.|.|.
+.L-J.
+.....
+4
+1
+===
+..F7.
+.FJ|.
+SJ.L7
+|F--J
+LJ...
+8
+1
+===
+...........
+.S-------7.
+.|F-----7|.
+.||.....||.
+.||.....||.
+.|L-7.F-J|.
+.|..|.|..|.
+.L--J.L--J.
+...........
+23
+4
+===
+..........
+.S------7.
+.|F----7|.
+.||OOOO||.
+.||OOOO||.
+.|L-7F-J|.
+.|II||II|.
+.L--JL--J.
+..........
+22
+4
+===
+.F----7F7F7F7F-7....
+.|F--7||||||||FJ....
+.||.FJ||||||||L7....
+FJL7L7LJLJ||LJ.L-7..
+L--J.L7...LJS7F-7L7.
+....F-J..F7FJ|L7L7L7
+....L7.F7||L7|.L7L7|
+.....|FJLJ|FJ|F7|.LJ
+....FJL-7.||.||||...
+....L---J.LJ.LJLJ...
+70
+8
+===
+FF7FSF7F7F7F7F7F---7
+L|LJ||||||||||||F--J
+FL-7LJLJ||||||LJL-77
+F--JF--7||LJLJ7F7FJ-
+L---JF-JLJ.||-FJLJJ7
+|F|F-JF---7F7-L7L|7|
+|FFJF7L7F-JF7|JL---7
+7-L-JL7||F7|L7F-7F7|
+L.L7LFJ|||||FJL7||LJ
+L7JLJL-JLJLJL--JLJ.L
+80
+10