Why Quick Sort preferred for Arrays and Merge Sort for Linked Lists?

Introduction to Why Quick Sort preferred for Arrays and Merge Sort for Linked Lists?

In this blog, we will learn Why Quick Sort preferred for Arrays and Merge Sort for Linked Lists, both Quick sort and merge sort is based on the divide and conquer algorithm. Quick sort does not divide the array into equal parts whereas merge sort divides the array into equal parts.

Why Quick Sort is preferred for Arrays?

  • One of the main reasons for efficiency in quick sort is locality of reference, which makes it easy for the computer system to access memory locations that are near to each other, which is faster than memory locations scattered throughout the memory which is the case in merge sort.
  • Quick sort is an in-place sorting algorithm i.e. it does not require any extra space, whereas Merge sort requires an additional linear space, which may be quite expensive. In merge sort, the allocation and deallocation of the extra space increases the running time of the algorithm.
  • The most practical implementation of Quick sort uses a randomized version which has an expected time complexity of O(NlogN). Although in the randomized version the worst case is possible, but for a particular pattern (like sorted array) the worst case doesn’t occur, and therefore the randomized quick sort works well in practice.

Why Merge Sort is preferred for Linked List?

  • Merge sort is preferred for linked list, the nodes may not be present at adjacent memory locations, therefore Merge Sort is used.
  • Unlike arrays, in linked lists, we can insert items in the middle in O(1) extra space and O(1) time if we are given a reference/pointer to the previous node. Therefore, we can implement the merge operation in the merge sort without using extra space.
  • Quick Sort requires a lot of access to different memory locations. To access ith index in a linked list, we have to travel each and every node from the head to ith node as we don’t have a continuous block of memory. Therefore, the overhead increases for quick sort. On the other hand, merge sort accesses data sequentially and the need for random access is low.

Conclusion

This blog tried to discuss the main reason behind why Quick Sort is preferred for Arrays and why merge sort is preferred for Linked List. we hope you will understand the reason in details. If you want read more about Linked List and want to solve more questions on linked list, which are curated by our expert mentors at PrepBytes, you can follow this link Linked List.

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FAQs

  1. Is merge sort preferred for arrays over linked lists?
  2. As we discussed above merge sort is preferred for linked list over arrays. Because linked lists take constant O(1) time and space complexity in insertion operation.

  3. What is the difference between quick sort and merge sort?
  4. Merge sort is based on divide and conquer algorithm which divides the array into parts then sort it accordingly, whereas quick sort sort the array by comparing each element with an element called pivot element.

  5. List the disadvantages of merge sort?
  6. Disadvantage of merge sort are as follows:

    • Merge sort requires extra space for storing the subarrays.
    • Merge sort is quite slow for small size array.
    • If the array is already sorted even then the algorithm does the whole process.
  7. Which algorithm is best for linked lists?
  8. Merge sort is best choice for sorting the linked lists. Because merge sort requires only O(1) extra space for implementation.

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