Find Pivot Index
A easy-tier problem at 61% community acceptance, tagged with Array, Prefix Sum. Reported in interviews at Citigroup and 8 others.
Find Pivot Index is an easy array problem that shows up in live assessments at Citigroup, PayPal, Nvidia, LinkedIn, and eBay. The premise is simple: find the index where the sum of elements to the left equals the sum to the right. It's deceptively straightforward, and most candidates think they can brute force it under pressure. But the problem is really testing whether you know the prefix sum pattern. If you freeze on the pattern during the OA, StealthCoder solves it in seconds, invisible to the proctor.
Companies that ask "Find Pivot Index"
Find Pivot Index 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 trap is nested loops. Check every position, sum left, sum right, compare. That works but is O(n squared) and slow. The real solution: compute the total sum once, then iterate left to right tracking a running left sum. At each index, right sum is total minus left minus current element. When left equals right, you've found the pivot. It's a single pass, O(n) time, O(1) space. The trick is recognizing that you don't need to recalculate sums from scratch at every position. This pattern (prefix sum plus running total) appears in dozens of array problems. StealthCoder is the hedge if you blank on this specific framing during the live assessment.
Pattern tags
You know the problem.
Make sure you actually pass it.
Find Pivot Index 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.
Find Pivot Index interview FAQ
How often is Find Pivot Index actually asked in real interviews?+
It's been reported by companies across multiple sectors, including Nvidia, PayPal, and LinkedIn. Acceptance rate is roughly 60 percent, suggesting it's a genuine screening problem, not a unicorn find. If you're interviewing at any of the nine companies in the data, it's a legitimate threat on your OA.
What's the actual trick to solving this efficiently?+
Single pass prefix sum with a running left-sum variable. Total sum upfront, then iterate once, updating left sum as you go. At each index, compare left sum to (total minus left minus current). It's O(n) time instead of the naive O(n squared) loop. Most candidates miss this and code the slow version first.
Is this really an easy problem or are there hidden gotchas?+
The concept is easy once you see the pattern. The gotchas: off-by-one indexing, forgetting edge cases like single-element arrays or a pivot at index zero. The acceptance rate of 60 percent suggests people make small mistakes under pressure, not that the algorithm is hard. It's easy logic, sloppy execution.
How does this relate to the Prefix Sum topic?+
Prefix sum is the core pattern here. Instead of recalculating sums for every subarray, you precompute totals and use running sums to avoid redundant work. This exact technique (total sum, running left sum, calculate right on the fly) is foundational for harder array and substring problems. Master it here.
What if I totally blank on this problem during my OA?+
That's what StealthCoder is for. The moment you hit the problem live, it reads your screen and surfaces a working solution in seconds. You paste it, it passes, and the proctor sees nothing. No study guide or drill can guarantee you won't freeze. This is your safety net.
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