Understanding Selection Sort Algorithm

Sorting algorithms are fundamental in computer science, and among them, the selection sort algorithm is one of the simplest to understand and implement. In this tutorial, we will explore how the selection sort algorithm works and guide you through the process of implementing it in Python.

What is Selection Sort?

The selection sort algorithm is a straightforward sorting technique that divides the input list into two parts: a sorted part and an unsorted part. The algorithm repeatedly selects the smallest (or largest, depending on the order) element from the unsorted part and moves it to the end of the sorted part.

Prerequisites

Before we dive into the implementation, make sure you have a basic understanding of:

• Python programming language
• Basic concepts of loops and conditionals

How Does Selection Sort Work?

To understand how selection sort works, let’s break it down into simple steps:

1. Start with the first element of the list, assuming it is the smallest.
2. Compare this element with all other elements in the list.
3. If a smaller element is found, update the index of the smallest element.
4. After completing the comparisons, swap the smallest element found with the first element.
5. Move to the next element and repeat the process until the entire list is sorted.

As you progress through the list, the number of comparisons decreases because the sorted part grows.

Implementing Selection Sort in Python

Now that we understand the concept, let’s implement the selection sort algorithm in Python step-by-step.

Step 1: Create the Main Loop

First, we need to create a variable to store our unsorted list. Then, we will create a loop that iterates through the length of the list.

nums = [4, 1, 5, 3, 2, 9, 7]

for x in range(len(nums)):
    min_index = x

Step 2: Add the Nested Loop

Next, we will add a nested loop that iterates through the unsorted part of the list, starting from the current index + 1.

nums = [4, 1, 5, 3, 2, 9, 7]

for x in range(len(nums)):
    min_index = x
    for y in range(x + 1, len(nums)):

Step 3: Create Conditional Statements

Within the nested loop, we will set a condition to check if the current element is less than the element at the minimum index. If it is, we will update the minimum index.

nums = [4, 1, 5, 3, 2, 9, 7]

for x in range(len(nums)):
    min_index = x
    for y in range(x + 1, len(nums)):
        if nums[y] < nums[min_index]:
            min_index = y

Step 4: Swap the Elements

After finding the minimum index, we will swap the elements at the current index and the minimum index.

nums = [4, 1, 5, 3, 2, 9, 7]

for x in range(len(nums)):
    min_index = x
    for y in range(x + 1, len(nums)):
        if nums[y] < nums[min_index]:
            min_index = y
    nums[x], nums[min_index] = nums[min_index], nums[x]

Step 5: Test the Code

Finally, we can print the sorted list to see the result of our selection sort implementation.

print(nums)

Conclusion

Congratulations! You have successfully implemented the selection sort algorithm in Python. This algorithm is not the most efficient for large datasets, but it is a great way to understand the fundamentals of sorting. Keep practicing, and you’ll become more comfortable with sorting algorithms and their implementations.

For further reading and resources, check out the links provided in the original article.

Source: Explore More…