Find Different Value
Reported by candidates from Doordash's online assessment. Pattern, common pitfall, and the honest play if you blank under the timer.
You've got a Doordash OA in the queue with a problem called Find Different Value reported this March. It's a straightforward pattern-matching question that tests your ability to spot the outlier in a dataset. Most candidates overthink it. The trick isn't complex logic, it's recognizing what makes one element stand out from the rest. StealthCoder is your safety net if you blank on the exact algorithm during the live assessment.
Pattern and pitfall
Find Different Value is fundamentally a hash-table or counting problem. The pattern is simple: iterate through the input, count occurrences of each element, then return the one that appears a different number of times than the others. The pitfall is trying to optimize prematurely or overthinking edge cases like empty inputs or arrays with all identical elements. In practice, a single pass with a frequency map solves it in O(n) time. The common variant is when one element appears once and all others appear twice, or vice versa. During your live OA, if you freeze on the exact approach, StealthCoder reads the problem statement and feeds you the frequency-map pattern in real time.
Drill it cold or hedge it with StealthCoder. Either way, don't walk into the OA hoping you remember the trick.
You can drill Find Different Value 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. Made for the candidate who got the OA invite this morning and has 72 hours, not six months.
Get StealthCoderRelated leaked OAs
This OA pattern shows up on LeetCode as single number. If you have time before the OA, drill that.
You've seen the question.
Make sure you actually pass Doordash's OA.
Doordash reuses patterns across OAs. Made for the candidate who got the OA invite this morning and has 72 hours, not six months. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Find Different Value FAQ
Is this an easy problem or a trick?+
It's straightforward. No trick. The challenge is reading carefully and handling the frequency count correctly. Most Doordash candidates solve it in under 5 minutes. The only trap is sloppy iteration or forgetting to check all elements before returning.
What data structure do I need?+
A hash table or dictionary. Count the frequency of each element, then iterate through and return the element with a frequency that differs from the rest. Python dict or defaultdict works perfectly.
Can I solve this without extra space?+
Not efficiently without extra space. A frequency map is O(n) space but O(n) time, which is optimal. Bit manipulation approaches exist but are slower and harder to code under pressure.
How should I structure my code?+
First pass: build a frequency map. Second pass: iterate the map and return the element whose count is unique. Edge case check: what if the input is empty or has only one element? Handle those before the main logic.
Is this problem still asked at Doordash?+
Yes, as of March 2024. It's a classic early-round OA problem. Doordash favors these straightforward counting and hash problems. If you see it, don't second-guess yourself. Solve it and move on.