2244 - Minimum Rounds to Complete All Tasks\.

Medium

You are given a 0-indexed integer array tasks, where tasks[i] represents the difficulty level of a task. In each round, you can complete either 2 or 3 tasks of the same difficulty level.

Return the minimum rounds required to complete all the tasks, or -1 if it is not possible to complete all the tasks.

Example 1:

Input: tasks = 2,2,3,3,2,4,4,4,4,4

Output: 4

Explanation: To complete all the tasks, a possible plan is:

• In the first round, you complete 3 tasks of difficulty level 2.

• In the second round, you complete 2 tasks of difficulty level 3.

• In the third round, you complete 3 tasks of difficulty level 4.

• In the fourth round, you complete 2 tasks of difficulty level 4.

It can be shown that all the tasks cannot be completed in fewer than 4 rounds, so the answer is 4.

Example 2:

Input: tasks = 2,3,3

Output: -1

Explanation: There is only 1 task of difficulty level 2, but in each round, you can only complete either 2 or 3 tasks of the same difficulty level. Hence, you cannot complete all the tasks, and the answer is -1.

Constraints:

• <code>1 <= tasks.length <= 10⁵</code>

• <code>1 <= tasksi<= 10⁹</code>