Java array sorting and index output: implementing test score sorting table

This document is intended to guide developers on how to sort array elements in Java programs and output the sorted results in tabular form while retaining the original index information. By modifying the existing `selectionSort` method and combining it with the index array, the test results input by the user are sorted and output, ensuring the accuracy and readability of the output results.

Problem analysis

The problem with the original program is that the selectionSort method directly sorts the array elements, causing the correspondence between the elements and the original index to be lost, and the sorted scores cannot be correctly output in the order of "Test 1" and "Test 2". At the same time, when sorting, the program needs to pay attention to sorting only the results actually entered by the user, not the entire array.

solution

In order to solve the above problem, we need the following steps:

1. Create an index array: Create an index array with the same size as the original score array, initialized from 0 to scoreCount-1.
2. Modify the sorting algorithm: Modify the selectionSort method so that it sorts the index array instead of directly sorting the score array. When comparing grades, use the index array to access the grade array.
3. Output the sorted table: When outputting the table, use the sorted index array to access the score array, thereby outputting the scores and corresponding test numbers in the sorted order.

Code implementation

Here is the modified code example:

 import java.util.Scanner;

public class ArrayIntro2 {

    public static void main(String[] args) {
        // integer array
        int[] TestGrades = new int[25];

        // creating object of ArrayIntro2T
        ArrayIntro2T pass = new ArrayIntro2T(TestGrades, 0, 0, 0);

        // getting total and filling array
        int scoreCount = ArrayIntro2T.FillArray(TestGrades, 0);

        //get average score
        double avg = pass.ComputeAverage(TestGrades, scoreCount);

        //outputting table
        ArrayIntro2T.OutputArray(TestGrades, scoreCount, avg);

        //outputting sorted table
        ArrayIntro2T.OutputSortedArray(TestGrades, scoreCount, avg);
    }

}

// new class to store methods
class ArrayIntro2T {
    // variable declaration

    doubleCalcAvg = 0;
    int ScoreTotal = 0;
    int ScoreCount = 0;
    int[] TestGrades = new int[25];

    // constructor
    public ArrayIntro2T(int[] TestGradesT, int ScoreCountT, double CalcAvgT, int ScoreTotalT) {
        TestGrades = TestGradesT;
        ScoreCount = ScoreCountT;
        CalcAvg = CalcAvgT;
        ScoreTotal = ScoreTotalT;

    }

    // method to fill array
    public static int FillArray(int[] TestGrades, int ScoreCount) {

        Scanner scan = new Scanner(System.in);

        System.out.println("Please enter test scores one at a time, up to 25 values ​​or enter -1 to quit");
        TestGrades[ScoreCount] = scan.nextInt();

        if (TestGrades[ScoreCount] == ​​-1) {
            System.out.println("You have chosen to quit ");
        }

        while (TestGrades[ScoreCount] &gt;= 0 &amp;&amp; ScoreCount <p> <strong>Code explanation:</strong></p><ol>
<li> <strong>OutputSortedArray method:</strong><ul>
<li> Create the index array indices and initialize it from 0 to scoreCount-1.</li>
<li> Call the selectionSort method and pass in the grade array, index array and number of grades.</li>
<li> Traverse the sorted index array, use TestGrades[indices[i]] to access the grades array, and output the grades and corresponding test numbers in the sorted order.</li>
</ul>
</li>
<li> <strong>selectionSort method:</strong><ul>
<li> Modify the sorting logic so that it sorts the index array.</li>
<li> When comparing grades, use TestGrades[indices[j]] and TestGrades[indices[minIndex]] to access the grade array.</li>
<li> Swap the elements in the index array instead of directly swapping the elements in the grades array.</li>
</ul>
</li>
</ol><h3> Running results</h3><p> The modified program can correctly output the sorted test score table and retain the original test number information.</p><h3> Things to note</h3>

• Ensure that the loop condition and array access method in the selectionSort method are correct to avoid array out-of-bounds errors.
• When outputting the table, use the sorted index array to access the score array to ensure the correct output order.
• The sorting algorithm can be modified according to actual needs, such as using more efficient sorting algorithms (such as quick sort, merge sort) to improve sorting efficiency.

Summarize

By creating an index array and modifying the sorting algorithm, we can sort the array elements in the Java program and output the sorted results in tabular form while retaining the original index information. This method can be applied to various scenarios where data needs to be sorted and the original order preserved.

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