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Python Bubble Sort

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Bubble Sort is a simple sorting algorithm that repeatedly compares and swaps adjacent elements if they are in the wrong order.

It's easy to understand but not efficient for large data.

🔹 How Bubble Sort Works

  1. Compare the first two elements

  2. Swap them if they are in the wrong order

  3. Move to the next pair and repeat

  4. Continue this process until the end of the list

  5. Repeat the process for all elements

🔹 Bubble Sort in Python

def bubble_sort(arr):
    n = len(arr)
    for i in range(n):
        for j in range(0, n - i - 1):
            if arr[j] > arr[j + 1]:
                arr[j], arr[j + 1] = arr[j + 1], arr[j]

Example

nums = [64, 34, 25, 12, 22, 11, 90]

bubble_sort(nums)
print("Sorted array:", nums)

✅ Output:

Sorted array: [11, 12, 22, 25, 34, 64, 90]

🔹 Optimized Bubble Sort (Early Stop)

def bubble_sort_optimized(arr):
    n = len(arr)
    for i in range(n):
        swapped = False
        for j in range(0, n - i - 1):
            if arr[j] > arr[j + 1]:
                arr[j], arr[j + 1] = arr[j + 1], arr[j]
                swapped = True
        if not swapped:
            break

This version stops if the array is already sorted — improves efficiency.

🔹 Time Complexity

Case Time
Best Case O(n)
Average O(n²)
Worst Case O(n²)
Space O(1)

Bubble sort is inefficient for large datasets.

🔹 Use Cases of Bubble Sort

  • Simple learning purposes

  • Small or mostly sorted lists

  • When simplicity matters more than speed

Practice Questions

Q1. Write a Python program to sort the list [5, 3, 8, 4, 2] using bubble sort.

Q2. Write a Python program to sort a list in descending order using bubble sort.

Q3. Write a Python program to count and display how many swaps were made during the bubble sort process.

Q4. Write a Python program to accept a list of numbers from the user and sort it using bubble sort.

Q5. Write a Python program to add a check in bubble sort to exit early if the list is already sorted.

Q6. Write a Python program to sort a list of strings alphabetically using bubble sort.

Q7. Write a Python program to print the list after each pass in the bubble sort algorithm.

Q8. Write a Python program to find and print the total number of passes (iterations) made by bubble sort.

Q9. Write a Python program to modify bubble sort to stop after k passes (take k as user input).

Q10. Write a Python program to measure and display the time taken to bubble sort a list of 1000 random numbers.

Python Bubble Sort Quiz

Q1: What does bubble sort do?

A. Splits list in half
B. Swaps adjacent elements
C. Uses a binary tree
D. Works on matrices

Q2: When does bubble sort stop early?

A. After 1 pass
B. After all are swapped
C. When no swaps are made
D. Never stops

Q3: Time complexity of bubble sort in worst case?

A. O(n)
B. O(log n)
C. O(n²)
D. O(n log n)

Q4: Space complexity of bubble sort?

A. O(1)
B. O(n)
C. O(n²)
D. O(log n)

Q5: What is swapped during sorting?

A. List names
B. Data types
C. Values
D. Indexes

Q6: How many passes needed to sort n elements?

A. 1
B. n
C. n - 1
D. n + 1

Q7: Bubble sort is best for:

A. Large datasets
B. Sorted or small lists
C. Binary trees
D. Hashing

Q8: Can Bubble Sort be used to sort strings?

A. No
B. Yes
C. Only numeric strings
D. Only if converted to ASCII

Q9: What is the key operation in bubble sort?

A. Binary division
B. Recursive calls
C. Comparing and swapping
D. Hash mapping

Q10: In Bubble Sort, what happens in the first pass?

A. Smallest element moves to the front
B. Largest element moves to the end
C. All elements get sorted
D. Middle element is fixed
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