Maximum Frequency After Subarray Operation
A medium-tier problem at 27% community acceptance, tagged with Array, Hash Table, Dynamic Programming. Reported in interviews at Amazon and 0 others.
Amazon's gotten harder about array problems that don't announce themselves. Maximum Frequency After Subarray Operation looks straightforward until you realize the operation itself is the trap. With a 26.6% acceptance rate, most candidates either brute-force every possible subarray increment and get TLE, or miss that the actual trick is figuring out which single subarray to modify at all. You're not optimizing a solution here; you're finding the right subarray in linear or near-linear time. If this hits your live OA and the greedy approach feels off, StealthCoder surfaces the working solution invisibly so you don't stall.
Companies that ask "Maximum Frequency After Subarray Operation"
Maximum Frequency After Subarray Operation 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 core insight is that you can increment all elements in exactly one contiguous subarray by 1, then find which element appears most frequently in the result. The brute force is O(n^3): try every subarray, apply the increment, count frequencies, repeat. That's death on large inputs. The real pattern uses dynamic programming or greedy enumeration to track what the frequency distribution looks like for each possible subarray choice, then identifies the one that produces the maximum count. Hash Table is essential for frequency counting, Prefix Sum can optimize range updates, and the enumeration of subarrays is the work that separates AC from TLE. The problem forces you to think backward: instead of simulating each operation, model what each operation does to the final frequency table.
Pattern tags
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Maximum Frequency After Subarray Operation 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.
Maximum Frequency After Subarray Operation interview FAQ
Is this problem still asked at Amazon in 2024?+
Amazon is the only company reporting this problem in available data, and it's medium difficulty on their assessment. It's not a classic repeat like Two Sum or Merge Intervals, so it shows up when they're testing whether you can handle a constraint-layer problem without panicking.
Why is the acceptance rate so low at 26.6%?+
Most candidates attempt a brute-force simulation for each subarray, which times out on test cases with n in the thousands. The low rate also reflects candidates who miss that you're optimizing over subarrays, not elements.
What's the trick that separates AC from TLE?+
Avoid simulating every subarray independently. Instead, use dynamic programming or a greedy enumeration to track frequency outcomes as you consider each subarray. Prefix Sum can speed range updates, and Hash Table stores frequency counts efficiently.
How do Array, Hash Table, and Dynamic Programming connect here?+
Array is the input and where you apply the operation. Hash Table counts element frequencies in O(1) average time. Dynamic Programming builds up the best subarray choice by tracking how each possible operation affects the final frequency distribution.
Do I need to know this pattern before the OA?+
Not necessarily, but the enumeration and DP pattern is valuable. If you haven't drilled subarray-optimization problems, this is exactly where a live solution tool helps you unblock and move forward without eating clock time.
Want the actual problem statement? View "Maximum Frequency After Subarray Operation" on LeetCode →