Grokking the Coding Interview: Patterns for Coding Questions

Find Non-Duplicate Number Instances (easy)

## Problem Statement

Given an array of sorted numbers, move all non-duplicate number instances at the beginning of the array in-place. The non-duplicate numbers should be sorted and you should **not use any extra space** so that the solution has constant space complexity i.e., $O(1)$.

Move all the unique number instances at the beginning of the array and after moving return the length of the subarray that has no duplicate in it.


**Example 1**:
```
Input: [2, 3, 3, 3, 6, 9, 9]
Output: 4
Explanation: The first four elements after moving element will be [2, 3, 6, 9].
```

**Example 2**:
```
Input: [2, 2, 2, 11]
Output: 2
Explanation: The first two elements after moving elements will be [2, 11].
```

**Constraints:**

- 1 <= nums.length <= 3 * 10<sup>4</sup>
- `-100 <= nums[i] <= 100`
- `nums` is sorted in non-decreasing order.

## Try it yourself   
Try solving this question here: