Developer Shares Space-Optimized Sliding Window Solution for Array Duplicate Problem

A developer published a space optimization approach for a classic array problem that checks whether two identical values exist within a given index distance k. The initial solution used a dictionary to store each element's last seen index, returning true if a duplicate was found within k steps. The improved approach replaces the dictionary with a fixed-size set, capping its length at k elements at any point during iteration. When the set exceeds k elements, the oldest entry is removed to maintain the window size. This sliding window technique reduces memory overhead by ensuring only a bounded number of values are stored at once.