Multi-Stream Round-Robin Iterator

Implement a merging iterator over multiple input streams that yields elements round-robin — one from each stream in turn, skipping exhausted streams. Supports has_next() and next(). The live trap is conforming to a provided base-class interface. Requirements Input: multiple streams / iterators (of bytes or chars), each exposing a sequential read interface. Implement a combined iterator that reads round-robin: one element from stream 0, one from stream 1, …, then back to stream 0. When a stream is exhausted, skip it on subsequent rounds. Expose has_next() and next(). Notes The core algorithm is simple: keep the live streams in a ring and advance an index, dropping a stream when it reports exhaustion. has_next() is true while any stream still has elements. The difficulty in the live round was the scaffolding, not the algorithm. The interviewer supplied a base stream class with fixed method signatures and required the solution to subclass it and match those signatures exactly — you cannot invent your own method names. Read the provided interface carefully and conform to it. Clarify the underlying stream interface up front: how exhaustion is signaled (exception vs sentinel vs a has_next on the stream itself) and the element type. Edge cases: some streams empty from the start, a single stream, ragged stream lengths. Preparation Implement the round-robin merge over a list of iterators with skip-on-exhaustion in under 20 minutes. Practice conforming to a given base-class interface (subclass + exact signature match) rather than designing your own. Pre-script clarifying questions about how the input streams signal end-of-stream.