Java Coding Test Course, Sorting Numbers 1

Hello! In this course, we will cover the basics of number sorting through algorithm problem solving using Java. Number sorting is one of the fundamental algorithms that frequently appears in programming problems and can be applied to various problem-solving scenarios. In this course, we will understand sorting algorithms through the “Sorting Numbers 1” problem and implement it in Java.

Problem Description

The goal of the problem is to sort the given numbers in ascending order. Here, the input consists of several numbers, and the process involves sorting these numbers and then outputting them. Understanding the basic concept of sorting algorithms and implementing it in Java is the core of this problem.

Problem Conditions

The number of input data is a natural number, and there may be duplicate numbers.
The count of the input numbers and the numbers themselves should be entered by the user.
The sorting criterion is ascending order, and the sorted results should be output.

Problem Solving Process

Step 1: Understanding the Problem

First, let’s take an example to understand the problem using the given numbers. For example, let’s assume the input numbers are as follows:

When we receive input like the above, our goal is to sort these numbers in ascending order and output them. Therefore, the output should look like this:

Step 2: Choosing a Sorting Algorithm

There are various methods to perform number sorting in Java. Representative sorting algorithms include bubble sort, selection sort, insertion sort, quick sort, and merge sort. The choice of algorithm can depend on the amount of data and its characteristics.

In this problem, we will use the simple selection sort algorithm. Selection sort works by repeatedly traversing the list, finding the smallest element at each step, and swapping it with the element at the current position.

Step 3: Implementing Selection Sort Algorithm

Now we will implement the selection sort algorithm in Java. Based on the concept of selection sort, we can write the following source code:


public class SortingExample {
    public static void main(String[] args) {
        // Sample data: input return array
        int[] arr = {5, 3, 8, 1, 2};
        selectionSort(arr); // Call sorting function
        printArray(arr); // Output sorted array
    }

    public static void selectionSort(int[] arr) {
        int n = arr.length; // Length of the array
        for (int i = 0; i < n - 1; i++) {
            int minIndex = i; // Index of current minimum value
            
            // Search for the minimum value in the remaining array
            for (int j = i + 1; j < n; j++) {
                if (arr[j] < arr[minIndex]) {
                    minIndex = j; // Update minimum value index
                }
            }
            // Swap minimum value with current value
            int temp = arr[minIndex];
            arr[minIndex] = arr[i];
            arr[i] = temp;
        }
    }

    public static void printArray(int[] arr) {
        for (int value : arr) {
            System.out.println(value); // Output array
        }
    }
}

Step 4: Analyzing the Code

Let’s analyze the code we wrote. The selectionSort method takes an array as a parameter and sorts it. First, it stores the length of the array in n, and then the outer loop traverses the array, setting the value at the current index as the reference. After that, the inner loop starts to find the minimum value in the remaining array and stores it in minIndex. Once the minimum value is found, it swaps the value at that index with the value at the current index to maintain the sorted state.

Step 5: Running the Results

Let’s run the code to check the sorting results. For the sample data {5, 3, 8, 1, 2}, if we perform selection sort, we can get the following result:

We can confirm that the sorting has been performed correctly in this way.

Conclusion

In this course, we implemented the selection sort algorithm through the “Sorting Numbers 1” problem using Java. Sorting algorithms are fundamental techniques that can be applied in various fields, and understanding their principles and implementation methods can greatly enhance programming skills. I hope you study various sorting algorithms and learn how to solve complex problems based on them.

Additional Learning Materials

If you would like to obtain more information about sorting algorithms, I recommend the following materials: