1582 articles
LeetCode 201 Bitwise AND of Numbers Range: AND every integer in [left, right] in O(log n). Master the common-prefix observation FAANG interviewers expect — far smarter than the obvious O(range) loop.
LeetCode 1879 Minimum XOR Sum of Two Arrays — pair every element of nums1 with a unique element of nums2 to minimize total XOR. Bitmask DP turns assignment into a 2^n state space. Step-by-step bit manipulation walkthrough for FAANG interviews.
LeetCode 89 Gray Code — generate an n-bit sequence where consecutive numbers differ by exactly one bit. The one-line XOR formula gray(i) = i XOR (i shifted right by 1) cracks it. FAANG-favorite bit manipulation interview problem.
LeetCode 187 Repeated DNA Sequences — find every 10-letter substring that appears twice or more. Encode each nucleotide in 2 bits, slide a 20-bit window with shift and AND. Linear-time bit manipulation interview classic.
LeetCode 1178 Number of Valid Words for Each Puzzle — count words containing the puzzle’s first letter using only puzzle letters. The 26-bit bitmask plus the (sub - 1) AND parent submask trick crushes a brute-force quadratic solution.