sorting three groups Leetcode Biweekly 111

2826. Sorting Three Groups

You are given a 0-indexed integer array nums of length n.

The numbers from 0 to n - 1 are divided into three groups numbered from 1 to 3, where number i belongs to group nums[i]. Notice that some groups may be empty.

You are allowed to perform this operation any number of times:

Pick number x and change its group. More formally, change nums[x] to any number from 1 to 3.
A new array res is constructed using the following procedure:

Sort the numbers in each group independently.
Append the elements of groups 1, 2, and 3 to res in this order.
Array nums is called a beautiful array if the constructed array res is sorted in non-decreasing order.

Return the minimum number of operations to make nums a beautiful array.