Leetcode 898. Bitwise ORs of Subarrays

Count how many distinct integers appear as the bitwise OR of any non-empty contiguous subarray of arr. Key insight: bitwise OR only accumulates bits so the number of distinct ORs ending at each position is bounded (≈bit-width of numbers), allowing an efficient iterative set-based accumulation for n up to 5·10^4 and values ≤ 10^9.