Intersection of Two Arrays
A easy-tier problem at 76% community acceptance, tagged with Array, Hash Table, Two Pointers. Reported in interviews at CVENT and 14 others.
Intersection of Two Arrays is an easy problem that shows up at major companies like Nvidia, PayPal, J.P. Morgan, and MongoDB. You need to find all elements present in both arrays, returning each common element once. It's a warm-up in most tech screens, but the trap is overthinking it or picking a slow approach under pressure. With 76% acceptance rate, candidates who nail this move fast to harder problems. If you freeze on array intersection logic during your assessment, StealthCoder surfaces a working solution instantly while the proctor sees nothing.
Companies that ask "Intersection of Two Arrays"
Intersection of Two Arrays 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 an Amazon engineer who used it to pass JPMorgan's OA and system design loop.
Get StealthCoderThe obvious approach uses a hash table: load one array into a set, iterate the other, and collect matches. Time complexity is linear. Some candidates waste effort sorting both arrays and using two pointers, which works but isn't optimal. Others try nested loops, which tanks on large inputs. The pattern is dead simple once you see it, but speed matters on live assessments. You'll also see binary search or sorting as interview variations to show you can think beyond brute force. StealthCoder is your safety net if the pattern doesn't click immediately during screen share. It handles all variants and avoids the silly mistakes that kill easy problems on OAs.
Pattern tags
You know the problem.
Make sure you actually pass it.
Intersection of Two Arrays 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 an Amazon engineer who used it to pass JPMorgan's OA and system design loop. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Intersection of Two Arrays interview FAQ
Why is this asked at companies like Nvidia and PayPal if it's just a hash table?+
It filters for baseline coding hygiene. Companies want to see clean, readable code and correct handling of edge cases (empty arrays, duplicates). It also lets interviewers assess if you can discuss trade-offs between hash, sort, and two-pointer approaches without prompting.
What's the trick if they ask me to optimize space without hash tables?+
Sort both arrays and use two pointers. This trades hash space for O(n log n) time, but uses O(1) extra space (excluding sort). Mention this variant unprompted if you want to show range. It's common follow-up reasoning at places like J.P. Morgan.
How do I avoid off-by-one errors and duplicates on the live assessment?+
Use a set to store the intersection result, not a list. This auto-dedupes. Test on a case where one array has duplicates: nums1 = [1, 2, 2, 1], nums2 = [2, 2]. Output should be [2], not [2, 2]. Many candidates slip here under time pressure.
Is Intersection of Two Arrays still asked at FAANG companies?+
Yes, frequently in phone screens or OA warm-ups. It's low-friction and lets interviewers see if you communicate clearly. At companies like MongoDB and Two Sigma, it's often part of a multi-problem set, so speed and correctness matter. You don't want to debug this in a live session.
Should I discuss the two-pointer approach even if hash is faster?+
Only if the interviewer hints at follow-ups or asks you to optimize further. Starting with hash table is the right move: it's O(n+m) time, easy to code, and bulletproof. Save two pointers for "what if we had limited memory" or to show algorithmic breadth if time allows.
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