Bubble Sort Algorithm and How does it work?

Bubble Sort is a simple sorting algorithm for sorting elements in a list into an ascending order. It steps through the list repeatedly, compares adjacent elements and swaps them if they are in the wrong order. The process keeps on going until all items are sorted.

How Does Bubble Sort Algorithm Work?

Let me try to break down the Bubble Sort process with a simple example

1. Initialization: Start with an unsorted list of elements.
2. Comparing Elements: Beginning from the first element, compare each pair of adjacent elements.
3. Swapping Elements: If a pair of elements is out of order, swap them.
4. Iterating Through the List: Move to the next pair and repeat the comparison and swap process.
5. Multiple Passes: Continue this process for the entire list. Each complete pass through the list places the next largest element in its correct position.
6. Stopping Condition: Repeat the passes until a complete pass is made without any swaps, indicating that the list is fully sorted.

Now consider this particular implementation of Bubble sort algorithm using python language.

def bubble_sort(arr):  
    n = len(arr)  
    for i in range(n):  
        # Track whether any swaps were made in this pass  
        swapped = False  
        for j in range(0, n - i - 1):  
            # Compare adjacent elements  
            if arr[j] > arr[j + 1]:  
                # Swap if elements are in the wrong order  
                arr[j], arr[j + 1] = arr[j + 1], arr[j]  
                # Mark that a swap has been made  
                swapped = True  
        # If no swaps were made, the list is already sorted  
        if not swapped:  
            break  
    return arr  
  
# Example usage  
numbers = [64, 34, 25, 12, 22, 11, 90]  
sorted_numbers = bubble_sort(numbers)  
print("Sorted array:", sorted_numbers)  

Let’s walk through each part of the program to understand how it functions:

1. Function Definition:  The function bubble_sort(arr) takes a list arr as input.
2. Length Calculation:  n = len(arr) calculates the length of the input list.
3. Outer Loop: for i in range(n):
   • This loop runs n times, where n is the number of elements in the list. Each iteration represents a pass through the list.
4. Swapped Flag: swapped = False
   • This flag is used to track whether any swaps were made during the current pass. If no swaps are made, the list is already sorted, and the algorithm can terminate early.
5. Inner Loop: for j in range(0, n - i - 1):
   • This loop iterates through the list, comparing adjacent elements. The range decreases with each pass because the largest elements “bubble” to the end of the list.
6. Comparison and Swap: if arr[j] > arr[j + 1]: arr[j], arr[j + 1] = arr[j + 1], arr[j] swapped = True
   • If the current element is greater than the next element, they are swapped. The swapped flag is set to True to indicate that a swap occurred.
7. Early Termination:if not swapped: break
   • If no swaps were made during the current pass, the list is already sorted, and the outer loop is terminated early.
8. Return Statement:return arr
   • The sorted list is returned.

Why Bubble Sort is Useful

While for large datasets this may not be the most efficient sorting algorithm, bubble sort has various applications and advantages that make it valuable to beginner programming.

1. Learning Fundamental Concepts
   • Bubble Sort can be an excellent introduction to learning sorting algorithms. The simplicity of Bubble sort makes it easy to understand and implement; hence, one can easily grasp complex algorithms after mastering it.
2. Sorting Small Datasets
   • In case of small datasets, a simple solution is provided by Bubble Sort. It works well when dealing with few elements.
3. Teaching Tool
   • This is because the Bubble Sort Algorithm has an intuitive nature which makes it a great teaching tool used in computer science courses. It assists students have a better understanding of how the basic elements of algorithm design as well as analysis work.
4. Nearly Sorted Data:
   • Bubble Sort Algorithm can be surprisingly efficient for datasets that are almost sorted already. In these cases, the algorithm can rapidly confirm the order with very few swaps.

Complexity and Performance Metrics

Understanding the performance of Bubble Sort Algorithm is crucial for evaluating its suitability for different tasks. Here’s a detailed breakdown

Time Complexity

• Best Case (Ω(n)): When the input list is already sorted, Bubble Sort Algorithm only needs to pass through the list once to confirm that no swaps are needed. In this case, the time complexity is linear, Ω(n).
• Average Case (Θ(n^2)): On average, Bubble Sort will compare each element with every other element, leading to a quadratic time complexity, Θ(n^2).
• Worst Case (O(n^2)): In the worst-case scenario, where the input list is sorted in reverse order, Bubble Sort will make the maximum number of comparisons and swaps, resulting in a quadratic time complexity, O(n^2).

Space Complexity

• Space Complexity (O(1)): Bubble Sort is an in-place sorting algorithm, meaning it requires only a constant amount of additional memory space.

Conclusion

Bubble Sort Algorithm may be the simplest of sorting algorithms, but its educational value is immense. By mastering Bubble Sort, you’ll gain a strong foundation in algorithmic thinking and problem-solving. As you progress in your programming journey, this understanding will pave the way for tackling more complex algorithms and challenges.

Remember, every expert was once a beginner. Happy coding!