Your question is Top-K Popular Items With Hash and Heap. Start with the requirements on the right.
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CloudKitchens needs to identify the most popular menu items from a massive stream of order events. Given item IDs and an integer k, return the k items with the highest frequencies using a hash map and a heap.
Return items ordered by decreasing frequency. If two items have the same frequency, return the smaller item ID first.
Implement top_k_items(item_ids, k), where item_ids is an iterable of non-negative integers representing ordered menu items and k is the requested number of results. Return a list of at most k item IDs. If fewer than k distinct items occur, return all distinct items.
The solution should count frequencies with a hash map and maintain a min-heap containing only the current top k items. The input may contain billions of events, so avoid sorting every event or storing unnecessary per-event data.
def top_k_items(item_ids, k):