Maximum Number of Events That Can Be Attended

Problem Given events [startDay, endDay], attend at most one event per day (an event can be attended on ANY single day in its range). Maximize events attended.

Input / Output

• Input: int[][] events. Output: max count attendable.

Constraints

• Up to 10^5 events, days up to 10^5; O(D log n) greedy expected.

Example

• [[1,2],[2,3],[3,4]] → 3 (days 1, 2, 3); [[1,2],[2,3],[3,4],[1,2]] → 4.