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Sorting algorithms in data structures: a closer look

by Akshay Sharma Tech Expert

There are different types of algorithms and one of them is the sorting algorithm. Sorting algorithms are a fundamental aspect of data structures and are used to order a collection of data in a specific way. Some common sorting algorithms include:


  • Bubble sort:


Bubble sort is a simple and intuitive sorting algorithm that repeatedly steps through a list of data, compares each pair of adjacent elements and swaps them if they are in the wrong order. It repeatedly goes through the list until no more swaps are needed, which indicates that the list is now sorted. The name "bubble sort" comes from the way that the larger elements "bubble" to the top of the list as the smaller elements "sink" to the bottom.


The basic idea of the algorithm is simple:


  1. It starts at the beginning of the list.

  2. Compare the first element with the next one.

  3. If the first element is greater than the next one, then swap them.

  4. Move to the next pair of elements and repeat step 3.

  5. Repeat steps 2-4 for all elements in the list.

  6. Repeat steps 1-5 until no more swaps are needed.


The time complexity of bubble sort is O(n^2) in the worst and average case and O(n) in the best case scenario when the input is already sorted. The best case occurs when the input is already sorted and no swapping is done.

Bubble sort is not commonly used in practice for large data sets because of its poor performance, but it can be useful for small data sets or as an educational tool for understanding the basic concepts of sorting algorithms.

It is easy to understand and implement, and it is often used as an introduction to sorting algorithms. It can also be used as a simple sorting algorithm for small data sets where performance is not a critical issue.


Insertion sort is a simple sorting algorithm that builds the final sorted list one item at a time by repeatedly taking the next unsorted item and inserting it into its correct position in the already sorted portion of the list. It is called insertion sort because it works by inserting each element in the correct position in the final sorted list, similar to how one might sort a hand of playing cards.

The basic idea of the algorithm is simple:


  1. It starts with an empty sorted list and an unsorted list containing all the elements.

  2. Take the first element from the unsorted list and insert it into the correct position in the sorted list.

  3. Repeat step 2 for all remaining elements in the unsorted list.


Insertion sort :


Insertion sort has a time complexity of O(n^2) in the worst and average case. However, it has a best-case time complexity of O(n) when the input is already sorted.

Insertion sort is not as efficient as other sorting algorithms such as quicksort or mergesort for large data sets, but it has some advantages over these algorithms in certain situations. For example, it is a good choice for small data sets or when the input is already partially sorted. It is also very efficient for data sets that are almost sorted and when the data is received in a streaming fashion.


Insertion sort is also very efficient in the case when the data is already sorted or almost sorted, because, in such cases, the number of inversions is low, and the algorithm performs well with fewer swaps.


Insertion sort is also very efficient when the data is almost sorted and it is received in a streaming fashion, because it can insert each element in its correct position as it is received, with only a few insertions and very few swaps.


Another use case of insertion sort is that it is used as a subroutine in other sorting algorithms like Shell sort and Tim sort.


Selection sort is a simple sorting algorithm that repeatedly selects the next smallest element from the unsorted portion of the list and appends it to the sorted portion. The basic idea of the algorithm is to divide the input list into two parts: the sorted portion and the unsorted portion. At each step, the algorithm finds the smallest element in the unsorted portion and moves it to the end of the sorted portion.


The basic idea of the algorithm is simple:


  1. It starts with an unsorted list of elements.

  2. Find the smallest element in the list.

  3. Swap the smallest element with the first element in the list.

  4. Repeat steps 2 and 3 for all remaining elements in the list.


The time complexity of the selection sort is O(n^2) in the worst, average and best cases. The time complexity and sorting algorithm's is a crucial one to observe. 


Selection sort is not as efficient as other sorting algorithms such as quicksort or mergesort for large data sets, but it has some advantages over these algorithms in certain situations. For example, it has a very small memory footprint and is easy to implement. It is also useful for small data sets or when the input is in a specific order, and it is relatively easy to understand and implement.


  • Selection sort

Selection sort is not used as often as other sorting algorithms in practice because of its poor performance, but it is still a good algorithm to know, especially if you're just getting started with sorting algorithms. It's also a good option if you have a small set of data and you don't have much memory to work with.

Selection sort is also useful in cases where the data is already sorted and the input is in a specific order, as it will perform well with fewer swaps.

Another use case of selection sort is that it is used as a subroutine in other sorting algorithms, such as the heapsort.


Some other sorting algorithms are-


  • merge sort: A divide and conquer algorithm that recursively breaks down the input list into smaller sublists, sorts them, and then merges them back together to form the final sorted list.

  • quicksort: Another divide and conquer algorithm that selects a "pivot" element from the input list and partitions the other elements into two groups: those less than the pivot, and those greater than the pivot. It then recursively sorts the two partitions.

  • Heapsort: A comparison-based sorting algorithm that builds a heap data structure out of the data being sorted and then repeatedly extracts the maximum element and places it at the end of the sorted list.

  • Radix sort: A non-comparison-based sorting algorithm that sorts data by grouping it based on the digits of its numerical values.


These are just a few examples of sorting algorithms, and each one has its strengths and weaknesses depending on the specific use case. 



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About Akshay Sharma Freshman   Tech Expert

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Joined APSense since, May 26th, 2022, From New Delhi, India.

Created on Feb 3rd 2023 00:22. Viewed 175 times.

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