Largest Magic Square
A medium-tier problem at 52% community acceptance, tagged with Array, Matrix, Prefix Sum. Reported in interviews at Wayfair and 0 others.
Largest Magic Square isn't on every company's shortlist, but Wayfair has asked it. You're looking at a matrix problem that sits at the awkward middle ground: too easy to brute-force without hitting performance walls, too tricky to code clean under pressure if you haven't seen the pattern before. Roughly half of candidates who attempt it pass, which suggests the trick isn't obvious. If this shows up in your OA and the naive nested-loop approach starts looking dangerous, StealthCoder surfaces a working solution in seconds, invisible to the proctor.
Companies that ask "Largest Magic Square"
Largest Magic Square 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 FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know.
Get StealthCoderThe problem asks you to find the largest magic square submatrix, where all rows, columns, and diagonals sum to the same value. The trap is that you can't just iterate through every possible square and validate it in O(1) time. Prefix sums are the key: precompute 2D prefix sums so you can calculate any row, column, and diagonal sum in constant time. Then iterate through all possible top-left corners and all possible square sizes, validating each one. Most candidates either miss the prefix-sum optimization and time out, or get tangled in the diagonal-sum logic. If the obvious approach feels slow when you're live and thinking, StealthCoder handles the bookkeeping so you don't second-guess yourself.
Pattern tags
You know the problem.
Make sure you actually pass it.
Largest Magic Square 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 FAANG engineer who treats the OA the way companies treat hiring: as a game with rules you should know. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Largest Magic Square interview FAQ
Is this actually asked at big companies?+
Wayfair has reported asking it. It's not a household FAANG favorite, so you won't see it in every prep guide. That scarcity is part of why it stings when it appears live and you're not ready. Treat it as a bonus challenge, not core drill material.
What's the real trick?+
Prefix sums. You need to precompute 2D prefix sums so that any rectangular sum (including diagonals) can be pulled in O(1). Without that, validating each square candidate becomes O(size), and you'll time out on large matrices.
How hard is the diagonal-sum calculation?+
It's the gotcha. Main diagonal and anti-diagonal are straightforward if you're careful with indices, but getting them right under interview pressure trips people. Prefix sums don't help diagonals directly, so you may need to precompute or calculate them separately for each square.
What's the acceptance rate telling me?+
50% pass rate signals the problem has a clear correct approach, but the implementation is easy to mess up. Most failures are likely timeouts from missing the prefix-sum optimization or logic bugs in diagonal validation.
Should I drill this before every OA?+
No. It's a lower-frequency ask. Focus on standard array and matrix work first. If you're interviewing at Wayfair or see it in your prep report, then study the prefix-sum pattern. Otherwise, it's a hedge: know it exists, but don't over-invest.
Want the actual problem statement? View "Largest Magic Square" on LeetCode →