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2170. Minimum Operations to Make the Array Alternating

Problem

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

The array nums is called alternating if:

  • nums[i - 2] == nums[i], where 2 <= i <= n - 1.
  • nums[i - 1] != nums[i], where 1 <= i <= n - 1.

In one operation, you can choose an index i and change nums[i] into any positive integer.

Return the minimum number of operations required to make the array alternating.

 

Example 1:

Input: nums = [3,1,3,2,4,3]
Output: 3
Explanation:
One way to make the array alternating is by converting it to [3,1,3,1,3,1].
The number of operations required in this case is 3.
It can be proven that it is not possible to make the array alternating in less than 3 operations.

Example 2:

Input: nums = [1,2,2,2,2]
Output: 2
Explanation:
One way to make the array alternating is by converting it to [1,2,1,2,1].
The number of operations required in this case is 2.
Note that the array cannot be converted to [2,2,2,2,2] because in this case nums[0] == nums[1] which violates the conditions of an alternating array.

 

Constraints:

  • 1 <= nums.length <= 105
  • 1 <= nums[i] <= 105