Find The Original Array of Prefix Xor
A medium-tier problem at 88% community acceptance, tagged with Array, Bit Manipulation. Reported in interviews at Morgan Stanley and 2 others.
You're given a prefix XOR array and need to reconstruct the original values. Morgan Stanley, Nvidia, and IBM have all asked this one. It's deceptively simple if you know the trick, brutal if you don't. The acceptance rate sits at 88 percent, which sounds high until you realize most candidates who nail it saw the pattern immediately while others waste 20 minutes chasing the wrong approach. The inverse relationship between XOR operations is the key that unlocks it. If this problem hits your live assessment and you blank on the reversal logic, StealthCoder solves it in seconds, invisible to the proctor.
Companies that ask "Find The Original Array of Prefix Xor"
Find The Original Array of Prefix Xor 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 engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage.
Get StealthCoderThe insight is that XOR is self-inverse. If you have prefix[i] = original[0] XOR original[1] XOR... XOR original[i], then original[i] = prefix[i] XOR prefix[i-1]. The first element is always prefix[0]. Most candidates get stuck trying to reconstruct forward or overthinking the state transitions. Once you see that each element depends only on two adjacent prefix values, the loop becomes trivial. The trap is implementation noise: off-by-one errors on indexing, forgetting the base case, or mishandling the first element. This is a Array and Bit Manipulation problem that tests whether you truly understand XOR properties or just pattern-match. StealthCoder is the hedge for the one interview where the pattern doesn't click under time pressure.
Pattern tags
You know the problem.
Make sure you actually pass it.
Find The Original Array of Prefix Xor 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. Built by an engineer who got tired of watching his cohort grind for six months and still get filtered at the OA stage. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Find The Original Array of Prefix Xor interview FAQ
Is this really asked at FAANG and major financial firms?+
Yes. Morgan Stanley, Nvidia, and IBM have reported it. The 88 percent acceptance rate suggests it's a medium-difficulty screening problem, not a 'gotcha' hard question. It's testing solid fundamentals in bit manipulation and array manipulation, not obscure knowledge.
What's the trick I'm missing if I can't solve it in 10 minutes?+
You're likely trying to reconstruct forward or looking for a complex DP state. The trick: XOR is reversible. prefix[i] XOR prefix[i-1] = original[i]. That's the whole pattern. Once you see it, code in under two minutes.
How does this relate to other bit manipulation problems?+
It's a pure XOR property play. Understanding that XOR cancels out (a XOR a = 0) and is associative is the foundation. If you're weak on XOR fundamentals, drill simpler XOR problems first. This one assumes you already know the rules.
Will the assessment test edge cases like single-element arrays?+
Almost certainly. A single-element prefix array means the original array is just that one element. Make sure your base case handles it cleanly. The problem is straightforward enough that edge cases are your main failure point.
Should I memorize this pattern or understand it?+
Understand it. You need to derive why XOR reversal works, not just recall the solution. If you can explain why prefix[i] XOR prefix[i-1] recovers the original, you'll solve variants and related problems confidently under pressure.
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