Find Duplicate File in System
A medium-tier problem at 68% community acceptance, tagged with Array, Hash Table, String. Reported in interviews at Dropbox and 2 others.
File system problems show up in Dropbox and Applied Intuition interviews because they test your ability to spot duplicates at scale. The challenge here isn't the algorithm, it's the parsing and hashing strategy. You've got a list of file paths with content hashes, and you need to find which files are actually identical. Most candidates waste time on the wrong data structure or misread the input format. If this problem hits your live OA and you blank on how to efficiently group files by content, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
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Find Duplicate File in System is the kind of problem that decides whether you pass. StealthCoder reads the problem on screen and surfaces a working solution in under 2 seconds. Invisible to screen share. The proctor sees nothing. Made by a working Amazon engineer who got tired of watching qualified friends bomb OAs they'd solve cold in an IDE.
Get StealthCoderThe trick is parsing the input correctly, then using a hash table to group files by their content hash. Each file entry contains a path and a content identifier. You iterate through, extract the content hash, and bucket files by that hash. Files with the same content hash are duplicates. The pitfall: over-complicating the grouping logic or trying to read file content when you're already given the hash. Hash Table is the core topic here; Array and String handle the parsing and output formatting. Acceptance sits at 67 percent, which means the pattern is straightforward once you see it, but parsing bugs sink half the candidates. This is exactly the type of problem where a live OA shows you a slightly different input format than your practice run, and you need a second to adapt. StealthCoder is your safety net for that moment.
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Find Duplicate File in System recycles across companies for a reason. It's medium-tier, and most candidates blank under the timer. StealthCoder is the hedge: an AI overlay invisible during screen share. It reads the problem and surfaces a working solution in under 2 seconds. Made by a working Amazon engineer who got tired of watching qualified friends bomb OAs they'd solve cold in an IDE. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Find Duplicate File in System interview FAQ
What's the actual trick to this problem?+
Group files by their content hash using a hash table, then return only groups with more than one file. The parsing is the real work. Read the input format carefully, extract path and hash separately, and bucket by hash value. Most duplicates are caught by the second file in each bucket.
Is this still asked at Dropbox and Applied Intuition?+
Yes. Dropbox, Applied Intuition, and Turing all report asking it. At 67 percent acceptance, it's a medium that interviews don't treat as trivial. The problem maps directly to their real file-comparison work, so expect variations on input format or the definition of duplicate.
What's the most common mistake candidates make?+
Misreading the input format or trying to parse file content when you're already given a content identifier. Others waste time with nested loops or unnecessary sorting. The hash table approach is linear once you've parsed correctly. Off-by-one errors in extracting the hash from each file path also burn time.
Do I need to sort the output or handle edge cases?+
Check the problem statement for output order. Most variants don't care about sort order, but some require lexicographic ordering of file paths within each duplicate group. Handle empty input and single-file cases. The content hash identifier is already unique per file, so collisions aren't a concern.
How does this relate to the Hash Table and Array topics?+
Hash Table groups files by content. Array is your output container for the list of duplicate lists. String handling comes in parsing the file path format. All three are equally weighted. If you nail the hash table design, the rest is straightforward iteration and formatting.
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