Selection Sort in Ascending Order in Java

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Selection Sort is another straightforward sorting algorithm. Its mechanism revolves around dividing the input list into two parts: a sorted and an unsorted region. The algorithm repetitively selects the smallest (or largest, depending on sorting order) element from the unsorted region and places it in the sorted region. 

In this post, we'll deep dive into how to implement the Selection Sort algorithm in Java for sorting elements in ascending order. We'll accompany the code with step-by-step explanations to ensure a thorough grasp of the concept. 

Java Program for Selection Sort in Ascending Order

public class SelectionSortAscending {

    public static void main(String[] args) {
        // Initialize a sample array of numbers
        int[] numbers = {64, 34, 25, 12, 22, 11, 90};

        // Sort the array using Selection Sort
        selectionSort(numbers);

        // Display the sorted array
        System.out.println("Sorted array in ascending order:");
        for (int num : numbers) {
            System.out.print(num + " ");
        }
    }

    /**
     * Perform selection sort on the given array in ascending order.
     *
     * @param arr The array to be sorted.
     */
    public static void selectionSort(int[] arr) {
        int n = arr.length;

        // One by one move the boundary of the unsorted sub-array
        for (int i = 0; i < n - 1; i++) {
            // Find the minimum element in the unsorted array
            int min_idx = i;
            for (int j = i + 1; j < n; j++) {
                if (arr[j] < arr[min_idx]) {
                    min_idx = j;
                }
            }

            // Swap the found minimum element with the first element of the sub-array
            int temp = arr[min_idx];
            arr[min_idx] = arr[i];
            arr[i] = temp;
        }
    }
}

Output: 

Sorted array in ascending order:
11 12 22 25 34 64 90

Step-by-Step Explanation: 

Initialization: We begin by defining a sample array of integers named numbers. 

Selection Sort Mechanism: The function selectionSort is where the magic happens. It sorts the provided array in ascending order using the Selection Sort algorithm. 

Finding the Minimum: For every pass, we locate the smallest element in the unsorted section of the array. This is achieved by iterating through the array and comparing elements. 

Swapping: Once we've identified the smallest element in the unsorted portion, we swap it with the first element of the unsorted section. With every iteration of the outer loop, the boundary of the sorted and unsorted sections changes, thus expanding the sorted section and shrinking the unsorted one. 

Displaying the Output: After the sorting is done, we loop through the numbers array and print out each number, which is now in ascending order. 

In essence, the Selection Sort algorithm, while simple, isn't the most efficient for large lists. However, due to its simplicity, it's often used as a teaching tool for beginners in computer science. With this walkthrough, you should now have a solid understanding of how Selection Sort operates, especially in Java. Happy coding!

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