Optimal Partition of String
A medium-tier problem at 78% community acceptance, tagged with Hash Table, String, Greedy. Reported in interviews at Docusign and 0 others.
Optimal Partition of String is a medium-difficulty greedy problem that tests whether you can spot the simple pattern before overthinking it. It's asking you to split a string into the minimum number of substrings where each substring contains no duplicate characters. Docusign has asked it. The acceptance rate is solid at 78%, which means most candidates who see it pass, but a chunk still blank on the greedy insight under timed pressure. If this problem hits your live assessment and you start building a complex state machine, StealthCoder surfaces the actual solution in seconds while the proctor sees nothing.
Companies that ask "Optimal Partition of String"
Optimal Partition of String 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. Built by a senior engineer who knows the OA is theater. This is the script.
Get StealthCoderThe trick is greedy: iterate through the string once and keep a hash table (or set) of characters in the current substring. The moment you hit a character already in that substring, you've hit the partition point. Push the current substring to your result, reset your hash table, and start a new substring from that character. The greedy choice is locally optimal and yields the globally optimal partition because every character must end up somewhere, and delaying a partition when a duplicate appears only wastes characters. Most candidates either try dynamic programming or attempt to look ahead, both overengineered. Hash Table and String are your tools; Greedy is the mindset. StealthCoder serves this pattern instantly if you freeze on the implementation under time pressure.
Pattern tags
You know the problem.
Make sure you actually pass it.
Optimal Partition of String 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. Built by a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Optimal Partition of String interview FAQ
Is this problem actually hard or just a pattern recognition check?+
Pure pattern recognition. Once you see the greedy approach, code is 8 to 10 lines. The hard part is not overcomplicating it under pressure. 78% acceptance confirms most people who stay calm pass. The 22% who fail usually tried DP or memoization unnecessarily.
Does this problem require advanced data structures?+
No. A hash table (or set) and a single pass is all you need. Some candidates use a character-to-index map for slight optimization, but the basic approach with a set is fast enough and cleaner. Docusign, the only reported asker, isn't testing your data structure library knowledge here.
What's the time and space complexity I should target?+
O(n) time where n is the string length (one pass). Space is O(k) where k is the alphabet size (26 for lowercase English). Hash Table makes this trivial. If your solution is worse, you're overcomplicating.
How does greedy differ from a sliding-window approach here?+
Greedy is simpler. You move a single pointer forward and partition the moment a duplicate appears. Sliding window tracks a range and shrinks/expands; it's overkill for this problem. Greedy gets the answer in one clean pass without the mental overhead of managing two pointers.
Is this problem still asked or is it outdated?+
Docusign has confirmed asking it. The pattern (greedy partition with a hash table) shows up across companies and online assessments. It's the type of problem that stays relevant because it's simple enough to verify under time pressure but easy to mess up if you panic.
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