first

1 files changed, 73 insertions, 0 deletions

diff --git a/2023/23/solve.py b/2023/23/solve.py
new file mode 100644
index 0000000..185328e
--- /dev/null
+++ b/2023/23/solve.py
@@ -0,0 +1,73 @@
+import sys
+
+sys.setrecursionlimit(100000)
+
+L = {
+    (y, x): c
+    for y, l in enumerate(open("input").readlines())
+    for x, c in enumerate(l.strip())
+    if c != "#"
+}
+
+
+def oob(y, x, d):
+    return (y, x) not in L
+
+
+def next(y, x, d):
+    if d == 0:
+        return (y - 1, x, d)
+    if d == 1:
+        return (y, x + 1, d)
+    if d == 2:
+        return (y + 1, x, d)
+    if d == 3:
+        return (y, x - 1, d)
+
+
+def neighbours(y, x, d):
+    ch = L[(y, x)]
+
+    if ch == "^":
+        return [next(y, x, 0)]
+    if ch == ">":
+        return [next(y, x, 1)]
+    if ch == "v":
+        return [next(y, x, 2)]
+    if ch == "<":
+        return [next(y, x, 3)]
+
+    return [next(y, x, 0), next(y, x, 1), next(y, x, 2), next(y, x, 3)]
+
+
+def dfs(y, x, d, v, p):
+    v.add((y, x))
+
+    ps = []
+    ns = neighbours(y, x, d)
+    for n in ns:
+        if (n[0], n[1]) not in v and not oob(*n):
+            np = p + [n]
+            ps.append(tuple(np))
+            ps.extend(dfs(*n, set(v), np))
+
+    return ps
+
+
+def solve1():
+    ps = dfs(0, 1, 2, set(), [(0, 1)])
+    mx = max(len(p) for p in ps)
+    print(mx - 1)
+
+
+# def solve2():
+#     res = 0
+#     for x in range(W):
+#         res = max(res, visited(0, x, 2), visited(H, x, 0))
+#     for y in range(H):
+#         res = max(res, visited(y, 0, 1), visited(y, W, 3))
+#     print(res)
+
+
+solve1()
+# solve2()