Efficiently Removing Duplicates from a Sorted Array
0 likes•66 views
The document provides a problem statement and solution walkthrough for removing duplicates from a sorted integer array in-place, maintaining the order of unique elements. It explains the algorithm using an example array, detailing the steps taken and how the modified array and the count of unique elements are derived. The final result reflects the unique elements at the beginning of the array, while the rest of the elements are deemed irrelevant.
![Example Walkthrough
Let's walk through an example with
the input array nums = [1, 1, 2, 2, 3,
4, 4].
Initial state:
• nums = [1, 1, 2, 2, 3, 4, 4]
• i = 0
• j starts at 1](https://image.slidesharecdn.com/q26-240531115616-88359ba5/85/Efficiently-Removing-Duplicates-from-a-Sorted-Array-6-320.jpg)
![Example Walkthrough
First iteration (j = 1):
• nums[1] (1) is equal to nums[0] (1)
• No changes, move to the next
iteration.](https://image.slidesharecdn.com/q26-240531115616-88359ba5/85/Efficiently-Removing-Duplicates-from-a-Sorted-Array-7-320.jpg)
![Example Walkthrough
Second iteration (j = 2):
• nums[2] (2) is different from
nums[0] (1)
• Increment i to 1
• Assign nums[2] (2) to nums[1]
• nums = [1, 2, 2, 2, 3, 4, 4]](https://image.slidesharecdn.com/q26-240531115616-88359ba5/85/Efficiently-Removing-Duplicates-from-a-Sorted-Array-8-320.jpg)
![Example Walkthrough
Third iteration (j = 3):
• nums[3] (2) is equal to nums[1] (2)
• No changes, move to the next
iteration.](https://image.slidesharecdn.com/q26-240531115616-88359ba5/85/Efficiently-Removing-Duplicates-from-a-Sorted-Array-9-320.jpg)
![Example Walkthrough
Fourth iteration (j = 4):
• nums[4] (3) is different from
nums[1] (2)
• Increment i to 2
• Assign nums[4] (3) to nums[2]
• nums = [1, 2, 3, 2, 3, 4, 4]](https://image.slidesharecdn.com/q26-240531115616-88359ba5/85/Efficiently-Removing-Duplicates-from-a-Sorted-Array-10-320.jpg)
![Example Walkthrough
Fifth iteration (j = 5):
• nums[5] (4) is different from
nums[2] (3)
• Increment i to 3
• Assign nums[5] (4) to nums[3]
• nums = [1, 2, 3, 4, 3, 4, 4]](https://image.slidesharecdn.com/q26-240531115616-88359ba5/85/Efficiently-Removing-Duplicates-from-a-Sorted-Array-11-320.jpg)
![Example Walkthrough
Sixth iteration (j = 6):
• nums[6] (4) is equal to nums[3] (4)
• No changes, end of the loop.](https://image.slidesharecdn.com/q26-240531115616-88359ba5/85/Efficiently-Removing-Duplicates-from-a-Sorted-Array-12-320.jpg)
![Example Walkthrough
The final modified array is nums = [1,
2, 3, 4, 3, 4, 4] and the new length is
i + 1 = 4.
The elements beyond the new length
(i.e., 3, 4, 4) are irrelevant as the
caller of the function is expected to
consider only the first i + 1 elements
as valid.](https://image.slidesharecdn.com/q26-240531115616-88359ba5/85/Efficiently-Removing-Duplicates-from-a-Sorted-Array-13-320.jpg)
Efficiently Removing Duplicates from a Sorted Array
- 1. Remove Duplicates from Sorted Array Eng Teong Cheah
- 2. Questions 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
- 3. Questions 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.
- 4. Demo
- 5. Solution
- 6. Example Walkthrough Let's walk through an example with the input array nums = [1, 1, 2, 2, 3, 4, 4]. Initial state: • nums = [1, 1, 2, 2, 3, 4, 4] • i = 0 • j starts at 1
- 7. Example Walkthrough First iteration (j = 1): • nums[1] (1) is equal to nums[0] (1) • No changes, move to the next iteration.
- 8. Example Walkthrough Second iteration (j = 2): • nums[2] (2) is different from nums[0] (1) • Increment i to 1 • Assign nums[2] (2) to nums[1] • nums = [1, 2, 2, 2, 3, 4, 4]
- 9. Example Walkthrough Third iteration (j = 3): • nums[3] (2) is equal to nums[1] (2) • No changes, move to the next iteration.
- 10. Example Walkthrough Fourth iteration (j = 4): • nums[4] (3) is different from nums[1] (2) • Increment i to 2 • Assign nums[4] (3) to nums[2] • nums = [1, 2, 3, 2, 3, 4, 4]
- 11. Example Walkthrough Fifth iteration (j = 5): • nums[5] (4) is different from nums[2] (3) • Increment i to 3 • Assign nums[5] (4) to nums[3] • nums = [1, 2, 3, 4, 3, 4, 4]
- 12. Example Walkthrough Sixth iteration (j = 6): • nums[6] (4) is equal to nums[3] (4) • No changes, end of the loop.
- 13. Example Walkthrough The final modified array is nums = [1, 2, 3, 4, 3, 4, 4] and the new length is i + 1 = 4. The elements beyond the new length (i.e., 3, 4, 4) are irrelevant as the caller of the function is expected to consider only the first i + 1 elements as valid.
- 14. CREDITS: This presentation template was created by Slidesgo, and includes icons by Flaticon, and infographics & images by Freepik Thanks! Do you have any questions? Please keep this slide for attribution
- 15. Resources Leetcode Q26 Remove Duplicates from Sorted Array