Count Max
Reported by candidates from IXL Learning's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
IXL Learning's 'Count Max' question hit candidates in March 2024, and it's deceptively simple on the surface. You're counting something to find a maximum value, but the trick is figuring out what you're actually counting and how to track it efficiently. Without the full problem text, the pattern is likely a hash table or prefix sum approach. If you blank during the live OA, StealthCoder runs invisibly on your screen to read the exact requirements and surface the solution in real time.
Pattern and pitfall
Count Max problems typically hide a frequency-counting or cumulative-tracking challenge. The naive approach is brute force: iterate, recount, repeat. The real solution uses a hash map to track frequencies or a prefix array to avoid recounting. The common pitfall is off-by-one errors when counting or comparing, and forgetting to handle edge cases like ties or empty inputs. During the OA, if you freeze on the logic, StealthCoder sits behind the screen, reads what you need to count, and gives you the pattern instantly so you can code without panic.
The honest play: practice the pattern, and have StealthCoder ready for the one you didn't see coming.
You can drill Count Max 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 for the candidate who saw this exact problem leak two days before his OA and wondered if anyone had a play.
Get StealthCoderRelated leaked OAs
This OA pattern shows up on LeetCode as majority element. If you have time before the OA, drill that.
You've seen the question.
Make sure you actually pass IXL Learning's OA.
IXL Learning reuses patterns across OAs. Built for the candidate who saw this exact problem leak two days before his OA and wondered if anyone had a play. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Count Max FAQ
Is this a hash table problem or math?+
Almost certainly hash table. You're likely building a frequency map, then iterating to find the key with the maximum count. The math angle is secondary. Keep space linear and time O(n) to O(n log n) depending on sorting.
What's the most common mistake candidates make?+
Not initializing the max value correctly or forgetting to compare all counts before returning. Also, not handling the case where multiple items have the same max count. Read the problem carefully for what to return in a tie.
Can I solve this in one pass?+
No. You need at least two: one to count frequencies, one to find the max. Some solutions sort the hash map by count, which adds O(n log n) but is still acceptable for IXL's constraints.
How much time do I have to solve this?+
IXL OAs typically give 60-90 minutes for 2-3 problems. Count Max alone is probably a 15-25 minute problem if you know the pattern. Don't overthink edge cases unless the prompt explicitly demands them.
Is this still being asked in 2024?+
Yes. Frequency counting and max-finding are evergreen. IXL focuses on these fundamentals. If you can solve this cleanly, you've covered a core pattern they care about.