bridge.xyz·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

May 2026

Summary

Coding round at bridge.xyz for a software engineer role. One question, file path simplification, which sounds like a warmup but has enough edge cases to trip you up if you're not careful about the stack logic.

Questions Asked (1)

Given an absolute Unix-style file path string, return the simplified canonical path. Handle '.', '..', consecutive slashes, and trailing slashes correctly. Walk through test cases and discuss time/space complexity.

Algorithms & Data Structures

Author's notes

I went straight to a stack and split on '/' which is the right call, but I fumbled the edge cases for a bit.

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AI HintsAI Generated

Suggested Approach

Use a stack to process each component of the path after splitting by '/'. For each component, ignore empty strings and '.', pop from the stack for '..' if possible, and push valid directory names. Finally, join the stack with '/' and prepend a leading slash to form the canonical path.

Pro tip: Explicitly discuss edge cases like root path '/', paths with only slashes, and paths that go above root (e.g., '/../'). Also, mention that the solution is O(n) time and O(n) space, and that you can optimize space by processing the string in one pass without splitting.

1. Clarify and Restate

Confirm the rules: '.' means current directory, '..' means parent, multiple slashes are treated as one, and trailing slashes are ignored. The result must start with '/' and not end with '/' unless it's the root.

2. Choose Data Structure

Use a stack (or list) to keep track of the valid directory names as you process each component. This naturally handles '..' by popping the last directory.

3. Process Components

Split the path by '/', iterate over each part: skip if empty or '.', pop if '..' and stack not empty, otherwise push the part onto the stack.

4. Build Result

Join the stack elements with '/' and prepend a leading '/'. If the stack is empty, return '/'.

5. Analyze Complexity and Test

State time complexity O(n) where n is the length of the path, and space O(n) for the stack and split array. Walk through test cases like '/home/', '/../', '/a/./b/../../c/', and '//'.

Key Points to Mention

Handling of '.' and '..' correctly, including when '..' is at root (should be ignored).
Ignoring empty components from consecutive or trailing slashes.
Using a stack to efficiently manage directory traversal.
Time complexity O(n) and space complexity O(n), with potential optimization to O(1) extra space if processing in-place.
Edge cases: root path '/', paths with only slashes, paths that go above root.
The final path must be canonical: starts with '/', no trailing '/', and no '.' or '..' components.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.