In-memory file system coding challenge (Perplexity)

Build a Node(name, is_dir, children, parent). Parse commands with split(). On every cd, traverse parent links and reject upward escapes from the working dir.

root = Node("/", True, {}, None)
cwd = root
for cmd in commands:
    parts = cmd.split()
    if parts[0] == "cd":
        cwd = resolve(cwd, parts[1])

Gotchas: not handling .. from root; case sensitivity (decide the policy upfront); paths containing spaces; not clamping recursion depth on deeply nested mkdir.