Remove Duplicates from Sorted Array II Leetcode Solution

In this post, we are going to solve the Remove Duplicates from Sorted Array II Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.

Table of Contents

Problem

Given an integer array nums sorted in non-decreasing order, remove some duplicates in-place such that each unique element appears at most twice. The relative order of the elements should be kept the same.

Since it is impossible to change the length of the array in some languages, you must instead have the result be placed in the first part of the array nums. More formally, if there are k elements after removing the duplicates, then the first k elements of nums should hold the final result. It does not matter what you leave beyond the first k elements.

Return k after placing the final result in the first k slots of nums.

Do not allocate extra space for another array. You must do this by modifying the input array in-place with O(1) extra memory.

Custom Judge:

The judge will test your solution with the following code:

int[] nums = [...]; // Input array
int[] expectedNums = [...]; // The expected answer with correct length

int k = removeDuplicates(nums); // Calls your implementation

assert k == expectedNums.length;
for (int i = 0; i < k; i++) {
    assert nums[i] == expectedNums[i];
}

If all assertions pass, then your solution will be accepted.

Example 1:

Input: nums = [1,1,1,2,2,3]
Output: 5, nums = [1,1,2,2,3,_]
Explanation: Your function should return k = 5, with the first five elements of nums being 1, 1, 2, 2 and 3 respectively.
It does not matter what you leave beyond the returned k (hence they are underscores).

Example 2:

Input: nums = [0,0,1,1,1,1,2,3,3]
Output: 7, nums = [0,0,1,1,2,3,3,_,_]
Explanation: Your function should return k = 7, with the first seven elements of nums being 0, 0, 1, 1, 2, 3 and 3 respectively.
It does not matter what you leave beyond the returned k (hence they are underscores).

Constraints:

1 <= nums.length <= 3 * 10⁴

-10⁴ <= nums[i] <= 10⁴
nums is sorted in non-decreasing order.

Now, let’s see the leetcode solution of Remove Duplicates from Sorted Array II Leetcode Solution.

Remove Duplicates from Sorted Array II Leetcode Solution in Python

class Solution:
  def removeDuplicates(self, nums: List[int]) -> int:
    i = 0

    for num in nums:
      if i < 2 or num != nums[i - 2]:
        nums[i] = num
        i += 1

    return i

Remove Duplicates from Sorted Array II Leetcode Solution in CPP

class Solution {
 public:
  int removeDuplicates(vector<int>& nums) {
    int i = 0;

    for (const int num : nums)
      if (i < 2 || num > nums[i - 2])
        nums[i++] = num;

    return i;
  }
};

Remove Duplicates from Sorted Array II Leetcode Solution in Java

class Solution {
  public int removeDuplicates(int[] nums) {
    int i = 0;

    for (final int num : nums)
      if (i < 2 || num > nums[i - 2])
        nums[i++] = num;

    return i;
  }
}

Note: This problem Remove Duplicates from Sorted Array II is generated by Leetcode but the solution is provided by Chase2learn This tutorial is only for Educational and Learning purposes.

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