Top-K Most Frequent Events

Problem Given a large stream of events, return the k most frequent event types by occurrence count.

Input / Output

• Input: a stream (or array) of event names, integer k.
• Output: the k event names with the highest counts (any order among equals).

Constraints

• The stream may be very large — potentially too large to keep every distinct key comfortably in memory.
• k is small relative to the number of distinct event types.

Example

• events = [a,b,a,c,a,b], k = 2 → [a, b] (counts a:3, b:2, c:1).