Find Good Subarray
Reported by candidates from TikTok's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
TikTok's August OA included a subarray problem with no explicit pattern hint, which means the trick is hidden in the constraints. You're looking at a problem where naive brute force will time out, and the real candidates either knew the optimization or they guessed. StealthCoder reads the full problem statement in real time and surfaces the pattern when your mind goes blank under pressure. The subarray class of problems always rewards pattern recognition over raw coding speed.
Pattern and pitfall
Without the exact problem text, 'good subarray' typically means you're either maximizing/minimizing a sum, finding a window that satisfies a condition, or counting valid ranges. The common pitfall: thinking you need nested loops when a sliding window or prefix sum will solve it in linear time. TikTok favors problems where the brute force is obvious but wrong. You'll either need a two-pointer or hash-table approach to track state as you move through the array. If it's about sum constraints, prefix sums plus a hash table turns it into a single pass. StealthCoder sits in the background and catches the moment you recognize the pattern, giving you confidence to code cleanly instead of second-guessing yourself.
If you see this problem in your OA tomorrow, the play is to recognize the pattern in 30 seconds. StealthCoder buys you that recognition.
You can drill Find Good Subarray cold, or you can hedge it. StealthCoder runs invisibly during screen share and surfaces a working solution in under 2 seconds. The proctor sees the IDE. They don't see what's behind it. Built by an Amazon engineer who passed his OA cold and still thinks the filter is broken.
Get StealthCoderRelated leaked OAs
This OA pattern shows up on LeetCode as max consecutive ones iii. If you have time before the OA, drill that.
You've seen the question.
Make sure you actually pass TikTok's OA.
TikTok reuses patterns across OAs. Built by an Amazon engineer who passed his OA cold and still thinks the filter is broken. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Find Good Subarray FAQ
What makes a subarray 'good' in TikTok's version?+
The problem statement defines it, but common definitions are: sum within a range, no duplicates, specific parity, or ratio-based. Read carefully. The definition is the entire puzzle. Once you know what 'good' means, the algorithm falls into place.
Is this a sliding window problem?+
Probably. If 'good' is a contiguous condition and the array is unsorted, sliding window or two-pointers is your first instinct. Expand right, shrink left when the window breaks the condition. O(n) is the target.
Will brute force pass?+
No. If you're iterating all subarray pairs, you'll hit time limit. TikTok expects linear or linearithmic. Assume n is up to 10^5. That means one or two passes, not nested loops.
Should I use a hash table?+
If 'good' involves tracking seen elements, duplicates, or counts, yes. A hash map of element frequencies or indices lets you prune the window in constant time per operation.
How do I prep in 48 hours?+
Memorize sliding window and prefix sum templates. Implement them twice without looking. Then solve one real subarray problem on any platform. The pattern matters more than drilling dozens.