Introduction to Bubble Sort Algorithm

Bubble Sort Algorithm (MIT OCW)
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Bubble Sort Algorithmic Dance
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Bubble Sort Algorithm Explained
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Have you ever watched bubbles rise to the surface of a drink? The larger bubbles tend to float up faster while smaller ones take their time. Bubble sort is a type of sorting algorithm which works in a similar way. It is one of the simplest sorting algorithms in computer science, making it a perfect starting point for understanding how sorting works. Before we dive into how Bubble Sort works, let’s first understand what sorting means and why it’s useful.

What is Sorting?

Sorting is the process of arranging data in a particular sequence or order, typically in ascending or descending order. It is a fundamental operation in computer science that we encounter daily, often without even realizing it!

For example, think about your everyday interactions with organized information. Whether you’re scrolling through your phone or shopping online, sorting plays a crucial role in making information accessible and meaningful. Here are some common examples you probably use regularly where sorting is applied:

  • Names in a contact list (alphabetical order)
  • Prices of products (lowest to highest)
  • Dates in a calendar (chronological order)
  • Test scores (highest to lowest)

When we sort data, we’re essentially organizing it in a way that makes it easier to search, analyze, and visualize. Whether you’re looking for a specific phone number in your contacts or finding the highest score in a game, sorting makes these tasks much more efficient.

What is Bubble Sort?

Bubble Sort is an algorithm used to sort a list of items by repeatedly comparing adjacent elements and swapping them if they are in the wrong order. The name “Bubble” in Bubble Sort comes from the way bigger elements in the array to be sorted “bubble” or move to the top of the list. This algorithm repeatedly steps through the list, compares adjacent elements, and swaps them if they are in the wrong order. It’s a simple and easy-to-understand algorithm, making it a great starting point for learning about sorting.

Intuitive example of how Bubble Sort Works

Here’s an intuitive example which explains how bubble sort works: Imagine you have a line of kids, and you want to arrange them from shortest to tallest. Here’s how you might do it using the Bubble Sort method:

  1. Start at the beginning: Look at the first two kids in line.

  2. Compare: If the first kid is taller than the second kid, swap their positions.

  3. Move to the next pair: Now, look at the second and third kids, and do the same comparison and swap if needed.

  4. Keep going: Continue this process until you reach the end of the line. After the first pass, the tallest kid will be at the end of the line.

  5. Repeat: Now, repeat the entire process, but this time, stop one position earlier (since the last kid is already in the correct spot).

  6. Continue repeating: Keep repeating this until everything is sorted. With each pass, the next tallest kid “bubbles” up to their correct position.

Below is the animation of this process:

For a more clearer step by step visualization and slide show of bubble sort algorithm, refer to this article: Bubble Sort Algorithm: Visualization and Animation.

Another example of how Bubble Sort Work

Let’s understand how bubble sort works with a simple example. Suppose we want to sort the list [5, 3, 8, 4, 6] in ascending order. Here’s how Bubble Sort would handle it:

  • First Pass:

    • Initial array: [5, 3, 8, 4, 6]
    • Compare 5 and 3: They’re out of order, so swap them
    • After swap: [3, 5, 8, 4, 6]
    • Compare 5 and 8: They’re in order, so no swap is needed
    • After comparison: [3, 5, 8, 4, 6]
    • Compare 8 and 4: They’re out of order, so swap them
    • After swap: [3, 5, 4, 8, 6]
    • Compare 8 and 6: They’re out of order, so swap them
    • After swap: [3, 5, 4, 6, 8]

    After the first pass, the largest number (8) has “bubbled” to the end of the list.

  • Second Pass:

    • Current array: [3, 5, 4, 6, 8]
    • Compare 3 and 5: They’re in order, so no swap is needed
    • After comparison: [3, 5, 4, 6, 8]
    • Compare 5 and 4: They’re out of order, so swap them
    • After swap: [3, 4, 5, 6, 8]
    • Compare 5 and 6: They’re in order, so no swap is needed
    • After comparison: [3, 4, 5, 6, 8]

    After the second pass, the second-largest number (6) is in its correct position.

  • Third Pass:

    • Current array: [3, 4, 5, 6, 8]
    • Compare 3 and 4: They’re in order, so no swap is needed
    • After comparison: [3, 4, 5, 6, 8]
    • Compare 4 and 5: They’re in order, so no swap is needed
    • After comparison: [3, 4, 5, 6, 8]

    Since no swaps are made in the last pass, the list can be considered as fully sorted: [3, 4, 5, 6, 8]

For more clearer explanation of how bubble sort algorithm works refer to this article: How Bubble Sort Works

Key Characteristics of Bubble Sort

  • Simple Implementation: Bubble sort is one of the easiest sorting algorithms to understand and implement, making it great for learning purposes.
  • In-Place Sorting: Bubble Sort doesn’t require extra memory to sort the list. It works directly on the original list. This makes it memory-efficient for small datasets.
  • Stable Sort: When bubble sort encounters equal elements, it maintains their relative positions in the final sorted array. This property is important when sorting objects with multiple attributes.
  • Comparison-Based: The algorithm makes decisions by comparing pairs of elements, making it work with any data type that can be compared (numbers, strings, custom objects, etc.).

What’s Next?

Now that you understand the basics of bubble sort, you might want to: