Given a sorted integer array arr in non-decreasing order, modify arr in-place so that each unique element appears only once, maintaining their original order. Return the number of unique elements, n. The first n elements of arr should contain the unique values in sorted order. Elements beyond index n-1 can be ignored.
Example 1
Input: [2,2,3,3,4,5,5]
Output: 4
Explanation: After removing duplicates, arr = [2,3,4,5,...], n = 4.
Example 2
Input: [-5,-5,-5,-5]
Output: 1
Explanation: After removing duplicates, arr = [-5,...], n = 1.
Example 3
Input: [7,8,9,10]
Output: 4
Explanation: No duplicates, arr = [7,8,9,10], n = 4.
Constraints
Case 1
Input: [1,1,1,2,2,3]
Expected: 3
Case 2
Input: [-2,-1,-1,0,0,0,1]
Expected: 4
Case 3
Input: [0,1,1,1,2,2,2,3,4,4]
Expected: 5
Case 4
Input: [100]
Expected: 1
Case 5
Input: [-100,-100,-99,-98,-98,-97]
Expected: 4