Bitwise ORs of Subarrays
A medium-tier problem at 41% community acceptance, tagged with Array, Dynamic Programming, Bit Manipulation. Reported in interviews at tcs and 0 others.
Bitwise ORs of Subarrays hits the problem list at medium difficulty with a 40% acceptance rate. You'll see it asked at TCS and similar companies hunting for candidates who understand the hidden structure of bit operations. The trap is obvious: iterate all subarrays, compute OR for each one, return the count of distinct values. That works on small inputs. On anything real, it times out. The pattern most candidates miss is that the number of distinct OR values across all subarrays ending at a single position is bounded far tighter than you'd expect. If you blank on this during the live assessment, StealthCoder surfaces the working solution in seconds, invisible to the proctor.
Companies that ask "Bitwise ORs of Subarrays"
Bitwise ORs of 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 core trick: as you extend a subarray by one element, the OR value either stays the same or jumps to a new value. It never decreases. More important, once you reach a position, the set of all possible OR values from subarrays ending at that position is small, roughly O(log max element). This means you don't enumerate all subarrays. Instead, you track distinct OR values as you slide through the array. Most candidates waste time on a brute-force subarray loop and hit time limits. The dynamic-programming insight is that you maintain only the unique OR values ending at each index, using a set to prune duplicates. When the obvious approach fails mid-interview, StealthCoder hedges you with the optimized solution so you don't tank the assessment on this specific problem.
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Bitwise ORs of Subarrays 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 a senior engineer who knows the OA is theater. This is the script. Works on HackerRank, CodeSignal, CoderPad, and Karat.
Bitwise ORs of Subarrays interview FAQ
Why does the brute force subarray approach fail here?+
Brute force iterates O(n^2) subarrays and computes OR for each in O(n) time, landing you at O(n^3). Even moderate input sizes exceed time limits. The constraint is hidden: the actual number of distinct OR values is logarithmic, not quadratic, because OR values converge quickly as subarrays grow.
What's the key insight to solve this efficiently?+
Track distinct OR values ending at each position using a set. As you move to the next element, compute OR of that element with all previous distinct values, plus the element itself. The set size stays small because repeated OR results compress. This cuts complexity from O(n^3) to O(n log M) where M is max element value.
Is this still asked in real company assessments?+
Yes. TCS reports it on their assessments. It's a medium-difficulty filter that separates candidates who understand bit manipulation properties from those who can only code brute force. Expect it in second-round or technical-screening interviews at mid-tier companies.
How do bit manipulation and dynamic programming connect here?+
Bit manipulation is the surface. Dynamic programming is the engine. You're not just computing ORs; you're building up the solution by tracking state (distinct OR values) at each position. The DP constraint is that the state set size is bounded, making the whole approach feasible.
What common mistakes sink candidates on this problem?+
Going straight to nested loops without recognizing the logarithmic bound on distinct values. Not using a set to track unique OR results per position. Trying to optimize array access instead of recognizing the real bottleneck is the number of unique OR values, not iteration count.
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