Sum of All Odd Length Subarrays
A easy-tier problem at 84% community acceptance, tagged with Array, Math, Prefix Sum. Reported in interviews at LinkedIn and 0 others.
Sum of All Odd Length Subarrays shows up in your LinkedIn assessment and it's deceptively easy to overthink. With an 83% acceptance rate, most people solve it, but many waste time on brute force when the math saves you completely. The problem asks you to sum all subarrays of odd length (1, 3, 5, etc.) in a single array. The trap is writing nested loops when a formula exists. If you hit this live and blank on the pattern, StealthCoder surfaces the working solution in seconds, invisible to the proctor.
Companies that ask "Sum of All Odd Length Subarrays"
Sum of All Odd Length Subarrays 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 brute force path is obvious: generate all subarrays, filter by odd length, sum them. That works and passes, but it's O(n squared) or worse. The real trick is prefix math. Each element contributes to the final sum a specific number of times based on how many odd-length subarrays include it. For each position, count how many odd-length subarrays contain that element, multiply by the element itself, and sum. The pattern emerges quickly once you see it: an element at index i is included in subarrays starting at positions 0 to i and ending at positions i to n-1. Track which combinations yield odd length and the contribution formula falls out. Most failures aren't wrong answers, they're time wasted on looping when StealthCoder runs the math path invisibly during your assessment and gives you the instant edge.
Pattern tags
You know the problem.
Make sure you actually pass it.
Sum of All Odd Length Subarrays recycles across companies for a reason. It's easy-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.
Sum of All Odd Length Subarrays interview FAQ
Is this problem actually easy or harder than the rating suggests?+
The 83% acceptance rate is honest. It's easy if you recognize the pattern or brute force passes. Hard if you freeze on optimization. The trick is mathematical not algorithmic, which trips up people trained on sorting and graphs. It's a pattern recognition problem masquerading as an array problem.
Should I code the brute force first or jump to the formula?+
Brute force is safe and correct. If you're confident on interviews, code it first, verify examples, then optimize. If you're under time pressure or don't see the pattern immediately, stay brute force. An O(n squared) solution that's correct and submitted beats nothing. The formula is faster but wrong code isn't worth it.
What's the connection between this problem and Prefix Sum?+
Prefix Sum is listed as a topic but isn't strictly required for the main solution. It appears if you use precomputation to speed up subarray queries. The real link is understanding cumulative contribution. Prefix Sum teaches you to think about aggregate values rather than individual operations, which is the mindset for the formula.
Does LinkedIn ask this differently in other interviews or is this the fixed version?+
We only have data on this specific problem from LinkedIn reports. Variants might exist, but this exact problem is what's documented. If you prepare for this version thoroughly, you're covering their pattern. They may ask it again or shift to a related contribution counting problem.
How should I practice this if the brute force approach is my safety net?+
Write brute force first, test on provided examples, then manually derive the contribution count for small arrays. Trace through one element and count manually how many odd-length subarrays contain it. The pattern clicks fast once you do it by hand. That manual work is better preparation than re-coding ten times.
Want the actual problem statement? View "Sum of All Odd Length Subarrays" on LeetCode →