Difference Between Bubble Sort and Selection Sort
Have you ever wondered about the distinctions between Bubble Sort and Selection Sort in sorting algorithms? Bubble Sort operates by repeatedly comparing and swapping adjacent elements to sort the list, akin to bubbles rising to the surface. On the other hand, Selection Sort methodically selects the minimum or maximum element from the unsorted segment of an array and positions it at the start or end of the sorted section, gradually sorting the entire array. Let's see in detail.
Sorting algorithms are methods used in computer science to rearrange a sequence of elements in a certain order, typically either ascending or descending. The importance of sorting lies in the fact that it makes data more understandable and easier to analyze. Sorting is also critical in many tasks, such as searching, data analysis, and algorithm optimization. In this blog, we will see the difference between selection sort and bubble sort in detail!
Table of Content
- Difference Between Bubble Sort and Selection Sort
- What is Bubble Sort?
- Time Complexity of Bubble Sort
- What is the Selection Sort?
- Time Complexity of Selection Sort
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Difference Between Bubble Sort and Selection Sort
Below is the table of differences between bubble sort and selection sort.
| Criteria |
Bubble Sort |
Selection Sort |
| Basic Concept |
Repeatedly steps through the list, compares adjacent elements and swaps them if they are in the wrong order. |
Divides the list into two parts: sorted and unsorted. Finds the smallest (or largest) element from the unsorted partition and moves it to the end of the sorted partition. |
| Performance on Nearly Sorted Data |
Performs well, as it requires fewer passes. It can be optimized to stop early if the list is sorted before the end is reached. |
No advantage on nearly sorted data; it will still go through the entire process of finding the minimum element and swapping. |
| Number of Swaps |
Performs many swaps, potentially as many as O(n²) in the worst case. |
Minimizes the number of swaps. At most, there will be n-1 swaps in the worst case. |
| Complexity in Best Case |
O(n) if optimized with a flag for a nearly sorted list. Otherwise, O(n²). |
Always O(n²), even if the list is already sorted. |
| Complexity in Average and Worst Case |
O(n²) due to repeated comparisons and swaps in the nested loops. |
O(n²), as it always searches for the minimum element for each position in the sorted partition. |
| Auxiliary Space |
O(1), as it is an in-place sorting algorithm with no need for additional storage. |
Also, O(1), as it sorts the list in place without additional memory. |
| Stability |
Stable - two objects with equal keys appear in the same order in the sorted list as they appear in the input list. |
Not stable - may change the order of elements with equal keys. |
| Adaptability |
Adapts to the context and can be optimized for better performance on nearly sorted lists. |
Not adaptive - the number of comparisons remains the same regardless of the initial order of elements. |
What is Bubble Sort?
Bubble Sort is a sorting algorithm frequently used for educational purposes due to its simplicity, though it's generally inefficient for large datasets. In Bubble Sort, the list is iterated by repeatedly comparing adjacent elements and swapping them if they are in the wrong order. This process continues until no more swaps are needed, which means the list is sorted.
During each pass through the list, the algorithm selects pairs of adjacent elements and compares their values. If a pair is in the wrong order (for instance, if the first element is larger than the second in an ascending sort), the algorithm swaps them. This action is repeated across the list, causing larger values to "bubble up" to the end of the list with each pass, similar to how bubbles rise to the surface of a liquid. The algorithm makes several passes through the list until it's fully sorted.
Time Complexity of Bubble Sort
| Case |
Time Complexity |
| Best Case |
O(n) |
| Average Case |
O(n²) |
| Worst Case |
O(n²) |
Read more about Bubble Sort Here
What is the Selection Sort?
Selection Sort is a sorting algorithm used for arranging a list or array of elements in a specific order (ascending or descending). The algorithm divides the input list into two parts: the sublist of items already sorted, which is built up from left to right, and the sublist of items remaining to be sorted that occupy the rest of the list. Initially, the sorted sublist is empty, and the unsorted sublist is the entire input list.
The algorithm works by repeatedly finding the smallest (or largest, depending on the sorting order) element from the unsorted sublist and swapping it with the leftmost unsorted element, placing it in the sorted sublist. This process continues by moving the boundary of the sorted and unsorted sublists, one element to the right each time. In essence, with each iteration, the Selection Sort algorithm selects the next smallest (or largest) element from the unsorted portion and moves it to its final position in the sorted portion.
Time Complexity of Selection Sort
| Case |
Time Complexity |
| Best Case |
O(n²) |
| Average Case |
O(n²) |
| Worst Case |
O(n²) |
Read more about Selection Sort Here
Thus, both Bubble Sort and Selection Sort are fundamental sorting algorithms with distinct characteristics, making them suitable for different scenarios, especially in educational contexts for teaching basic algorithm concepts. However, their inefficiency in handling large datasets limits their practical use in real-world applications.
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FAQs
What is Bubble Sort and Selection Sort, and how do they work?
Bubble Sort and Selection Sort are both sorting algorithms used to arrange elements in a specific order. Bubble Sort compares adjacent elements and swaps them if they are in the wrong order, while Selection Sort iterates through the array and selects the smallest (or largest) element and places it at the beginning (or end) of the array.
How do Bubble Sort and Selection Sort differ in terms of algorithmic complexity?
Bubble Sort has a time complexity of O(n^2) in the average and worst-case scenarios, making it inefficient for large datasets. Selection Sort also has a time complexity of O(n^2), making it similarly inefficient for large datasets, but it generally performs better than Bubble Sort due to fewer swaps.
What is the main difference in the approach of Bubble Sort and Selection Sort?
The main difference lies in their approach to sorting. Bubble Sort compares adjacent elements and moves the largest (or smallest) element to its correct position in each pass. Selection Sort, on the other hand, selects the smallest (or largest) element and places it at the beginning (or end) of the array in each iteration.
Which sorting algorithm is more suitable for small datasets?
Bubble Sort is often preferred for small datasets due to its simplicity and ease of implementation. However, Selection Sort may be slightly more efficient for small datasets because it requires fewer swaps compared to Bubble Sort.
In what scenarios would you choose Bubble Sort over Selection Sort, and vice versa?
Bubble Sort may be chosen when simplicity is preferred or when sorting small datasets. Selection Sort may be preferable when minimizing the number of swaps is important, or when implementing an in-place sorting algorithm without using additional space.
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