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.
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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. ++ +
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Constraints:
+ +1 <= tasks.length <= 1051 <= tasks[i] <= 109