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Remove Duplicates from Sorted Array

Easy
Two Pointers

Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order of the elements should be kept the same. Then return the number of unique elements in nums.

Consider the number of unique elements of nums to be k, to get accepted, you need to do the following things:

• Change the array nums such that the first k elements of nums contain the unique elements in the order they were present in nums initially. • The remaining elements of nums are not important as well as the size of nums. • Return k.

Example 1

Input: nums = [1,1,2]
Output: 2, nums = [1,2,_]
Explanation: Your function should return k = 2, with the first two elements of nums being 1 and 2 respectively. It does not matter what you leave beyond the returned k.

Example 2

Input: nums = [0,0,1,1,1,2,2,3,3,4]
Output: 5, nums = [0,1,2,3,4,_,_,_,_,_]
Explanation: Your function should return k = 5, with the first five elements of nums being 0, 1, 2, 3, and 4 respectively.

Constraints

  • •1 <= nums.length <= 3 * 10^4
  • •-100 <= nums[i] <= 100
  • •nums is sorted in non-decreasing order.
Show Hints (3)
Hint 1: Use two pointers: one for iterating through the array, one for tracking the position to place unique elements.
Hint 2: The slow pointer marks the position of the last unique element, while the fast pointer scans through the array.
Hint 3: When you find a new unique element (different from the one at slow pointer), increment slow and copy the element there.
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