I went with a stack pretty quickly, split both strings on '/' and processed tokens one by one.
Clarify assumptions about the input format (e.g., absolute current directory, relative destination) and edge cases. Then, describe a stack-based approach: split the current directory and destination by '/', process each component, and build the final path. Finally, discuss handling of edge cases like root directory and trailing slashes.
Pro tip: Mention that you would use a stack to efficiently handle '..' by popping the last directory, and emphasize the importance of normalizing the path to avoid redundant slashes and '.' components.
Confirm that the current directory is an absolute path and the destination is relative. Discuss edge cases such as empty destination, root directory, and multiple slashes.
Use a stack (or list) to represent the path components. This allows efficient handling of '..' by popping the last component.
Split both paths by '/', iterate through components, and for each: ignore '.' and empty strings, pop for '..' (if stack not empty), otherwise push the component.
Join the stack components with '/' and prepend a leading '/'. Ensure the result is absolute and handle the root case (empty stack yields '/').
Walk through examples like current='/a/b/c', dest='../../d' to verify correctness, and discuss time/space complexity (O(n) time, O(n) space).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
This was mostly a preprocessing step before feeding into the same normalizer.
Start by clarifying the current implementation of cd() and the expected behavior for absolute paths and ~. Then outline a step-by-step algorithm that handles path resolution, including edge cases like ~user and relative paths. Finally, discuss trade-offs and potential pitfalls, such as path normalization and platform differences.
Pro tip: Mention that you would use a well-tested library function like realpath or path.resolve to handle path normalization, but be prepared to explain how you would implement it from scratch if asked. This shows you value both correctness and understanding of fundamentals.
Ask questions to understand the existing cd() implementation, the environment (e.g., shell, OS), and any constraints. Confirm that absolute paths start with '/' and ~ expands to the user's home directory.
Outline how to detect and handle absolute paths and ~. For ~, expand to the home directory (e.g., via environment variable HOME or getpwuid). For absolute paths, use them directly. For relative paths, combine with current working directory.
Consider edge cases like ~user, trailing slashes, symbolic links, and path normalization (e.g., resolving '..' and '.'). Decide whether to normalize before changing directory or rely on the OS.
Write pseudocode or actual code, then walk through test cases: absolute path, ~, ~/subdir, relative path, and invalid paths. Ensure error handling for non-existent directories.
Talk about trade-offs: using built-in functions vs. manual parsing, security considerations (e.g., path injection), and portability across systems.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Clarify the function signature and symlink resolution semantics, then design an algorithm that iteratively resolves symlinks while tracking visited paths to detect cycles. Implement and test with edge cases like self-loops, multi-step cycles, and non-existent targets.
Pro tip: Explicitly discuss the trade-off between eager resolution (resolving all symlinks upfront) and lazy resolution (resolving on demand), and mention that cycle detection is typically done with a visited set or Floyd's cycle-finding algorithm.
Ask whether symlinks can be relative or absolute, whether the dictionary maps paths to targets, and what should happen if a symlink target doesn't exist. Confirm that cycles must be detected and reported.
Iteratively resolve symlinks: start with the input path, while the current path is a symlink, look up its target in the dictionary. Keep a set of visited paths to detect cycles. If a cycle is found, return an error or raise an exception.
Consider self-referential symlinks, multi-step cycles, symlinks pointing to non-existent paths, and paths that are not symlinks. Also consider relative symlink targets and how they resolve relative to the symlink's directory.
Write clean code with clear variable names. Test with a variety of cases: simple symlink, chain of symlinks, cycle, missing target, and non-symlink path. Use unit tests to verify behavior.
Discuss time and space complexity: O(n) time where n is the number of symlinks in the chain, O(n) space for the visited set. Mention alternative approaches like Floyd's algorithm for O(1) space, and when each is appropriate.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
I knew the built-in answer: a child process can't change the parent's working directory, so if cd ran as a subprocess the shell would be unaffected.
Start by explaining that cd must be a shell built-in because it changes the shell's own working directory, which a child process cannot do. Then describe how the OS resolves paths using inodes, covering directory entries, inode tables, and the step-by-step lookup process.
Pro tip: Mention that even if cd were an executable, it would only change its own working directory, not the parent shell's, because each process has its own current working directory. This shows deep understanding of process isolation.
State that cd modifies the shell's current working directory, which is a per-process attribute. A standalone executable runs in a child process, so any directory change would not affect the parent shell.
Give an example like ls, which can be an external executable because it doesn't need to change the shell's state. This highlights the distinction between commands that modify shell state and those that don't.
Explain that the kernel resolves a path by starting from the root (or current directory) and traversing each component. For each component, it looks up the name in the directory's entries to find the corresponding inode number.
Once the inode number is found, the kernel accesses the inode to get metadata and data block pointers. This process repeats for each path component until the final file's inode is reached.
Conclude that inodes are the fundamental data structure for file representation, and path resolution is essentially a series of directory lookups mapping names to inodes.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.