You are given an array of events where events[i] = [startDayi, endDayi]. Every event i starts at startDayi and ends at endDayi.
You can attend an event i on any day d where startDayi <= d <= endDayi. You can only attend one event at any time d.
Return the maximum number of events you can attend.
This is a classic greedy scheduling problem. Sort events by start day, then scan days in order while keeping all currently available events in a min-heap keyed by end day. Each day, attend the event that ends soonest to maximize future flexibility. The standard solution uses sorting plus a priority queue and runs in about O(n log n).
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