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Remove Duplicates from Sorted Array Test | Pre-employment assessment - Testlify
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Remove Duplicates from Sorted Array Test

Overview of Remove Duplicates from Sorted Array Test

The goal of the problem is to remove all the duplicated present in an array.

Skills measured

  • Two pointers
  • greedy

Available in



Coding Test


20 Mins





Use of Remove Duplicates from Sorted Array test

The solution to the problem implements a funtion which returns an integer representing the length of the modified vector after removing any number of duplicates.
The function begins with a check to see if the size of the input vector nums is less than or equal to 1. If it is, then there are no duplicates to remove, and the function simply returns the size of the vector.
If the size of nums is greater than 1, the function proceeds with the duplicate removal process. It initializes two variables: slow and fast. slow represents the index of the last non-duplicate element found so far, and fast is used to iterate through the vector to find duplicates.
The function enters a loop that continues until fast reaches the end of the vector (n is the size of nums). Inside the loop, it checks if the current element (nums[fast]) is equal to the previous element (nums[fast - 1]). If they are equal, it means a duplicate is found.
If a duplicate is found, the code enters another inner loop with the condition if (++fast >= n) break;. This loop increments fast until it finds the next non-duplicate element or reaches the end of the vector. This ensures that fast is pointing to the first occurrence of a non-duplicate element after the series of duplicates.
After exiting the inner loop, the code checks if fast is still less than the size of the vector (fast < n). If it is, it means a non-duplicate element was found after the series of duplicates. In this case, it assigns the value of this non-duplicate element to nums[++slow], effectively moving the non-duplicate element to the next position in the vector.
The outer loop continues, and the process repeats for the next set of duplicates or non-duplicate element.
Finally, the function returns slow + 1, which represents the length of the modified vector after removing duplicates. Adding 1 is necessary because slow represents the index of the last non-duplicate element, not the length of the vector itself.

Relevant for

  • Software Developer Engineer
  • Software Developer
  • Software Engineers

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Two pointers

The Two Pointers technique in the "Remove Duplicates from Sorted Array" problem involves using two pointers to iterate through the array. One pointer is used to track the current element being evaluated, while the other pointer is used to track the index where the next non-duplicate element should be placed. This technique is important because it allows us to efficiently remove duplicates in-place without using extra space. By utilizing two pointers, we can compare adjacent elements and only move the non-duplicate elements to the front of the array, thus achieving the desired result in linear time complexity.



The greedy skill covered in the Remove Duplicates from Sorted Array problem involves efficiently removing duplicate elements from an array without using extra space. This skill is important because it allows for a more optimized solution that reduces the time and space complexity of the algorithm. By greedily iterating through the array and comparing adjacent elements to determine if they are duplicates, we can remove them in-place without needing additional memory. This ensures that the array remains sorted and compact, without any unnecessary duplicate elements.

The Remove Duplicates from Sorted Array test is created by a subject-matter expert

Testlify’s skill tests are designed by experienced SMEs (subject matter experts). We evaluate these experts based on specific metrics such as expertise, capability, and their market reputation. Prior to being published, each skill test is peer-reviewed by other experts and then calibrated based on insights derived from a significant number of test-takers who are well-versed in that skill area. Our inherent feedback systems and built-in algorithms enable our SMEs to refine our tests continually.

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