divide and conquer plus bit manipulation Pattern

Recognition Signals

• Expect candidates to recognize bit-level patterns and swap sequences.
• Look for proper handling of masks and shifts without off-by-one errors.
• The interviewer wants bit-level reasoning, not string conversion or decimal digit counting.

Solve Flow

1. 1. Define the active state/window.
2. 2. Update state while preserving invariants.
3. 3. Validate with edge-heavy examples.

Common Misses

• Incorrectly swapping bits without using proper masks leading to wrong output.
• Counting decimal 1s in the number instead of set bits in the binary representation.