This Python function, `removeDuplicates`, accepts a list of integers (`nums`)...

This Python function, removeDuplicates, accepts a list of integers (nums) as input and removes duplicates, modifying the list in-place and returning the number of unique elements. Here's what the code does step by step:

1. Remove Duplicates Using set:

   • The set(nums) operation creates a set from the input list nums, automatically removing any duplicate values since a set only stores unique elements.

2. Sort the Unique Elements:

   • The sorted(set(nums)) ensures the unique elements are returned in sorted (non-decreasing) order.

3. Modify nums In-Place:

   • The nums[:len(unique)] = unique line updates the first len(unique) elements in the original nums list to the sorted unique elements using slicing. The remaining elements in the list (if any) are untouched but effectively ignored.

4. Return the Count of Unique Elements:

   • The function returns the length of the unique list (i.e., the number of unique elements in the input).

Example:

solution = Solution()
nums = [1, 1, 2, 2, 3]
result = solution.removeDuplicates(nums)
print(result)  # Output: 3
print(nums)    # Output: [1, 2, 3, _, _] (_ represents unmodified positions in the original list)

Summary:

This code effectively removes duplicates in a sorted manner and modifies the input list nums in-place, returning the count of unique elements. Note that the original list may still retain old values beyond the range of unique elements, but those are no longer considered relevant.