2870 - Minimum Number of Operations to Make Array Empty.

Medium

You are given a 0-indexed array nums consisting of positive integers.

There are two types of operations that you can apply on the array any number of times:

• Choose two elements with equal values and delete them from the array.

• Choose three elements with equal values and delete them from the array.

Return the minimum number of operations required to make the array empty, or -1 if it is not possible.

Example 1:

Input: nums = 2,3,3,2,2,4,2,3,4

Output: 4

Explanation: We can apply the following operations to make the array empty:

• Apply the first operation on the elements at indices 0 and 3. The resulting array is nums = 3,3,2,4,2,3,4.

• Apply the first operation on the elements at indices 2 and 4. The resulting array is nums = 3,3,4,3,4.

• Apply the second operation on the elements at indices 0, 1, and 3. The resulting array is nums = 4,4.

• Apply the first operation on the elements at indices 0 and 1. The resulting array is nums = [].

It can be shown that we cannot make the array empty in less than 4 operations.

Example 2:

Input: nums = 2,1,2,2,3,3

Output: -1

Explanation: It is impossible to empty the array.

Constraints:

• <code>2 <= nums.length <= 10⁵</code>

• <code>1 <= numsi<= 10⁶</code>