How do you compute the bitwise AND of all integers in an inclusive range [m, n]?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
While n > m, clear the lowest set bit of n with n &= n-1
WHY — Bit Manipulation instead of guessing?
Why interviewers care about Bit Manipulation:
question about Bit Manipulation.
trade-offs, and what you would actually do on a DSA project - not buzzwords.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1While n > m,
clear the lowest set bit of n with n &= n-1
- 2the surviving prefix is
the AND of the range because any differing low bit is zeroed by a carry in the range.
- 3Time is O(number of
low bits cleared), at most 32, space O(1).
- 4Shifting both until they
match also finds the common prefix.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
While n > m, clear the lowest set bit of n with n &= n-1 the surviving prefix is the AND of the range because any differing low bit is zeroed by a carry in the range.