找到矩阵的最大元素并删除具有该元素的行

Question

我需要帮助来完成删除具有最大元素的行。我设法读取用户的输入以设置矩阵维度，用随机数填充矩阵并搜索最大元素。但是，我无法删除具有最大元素的行。

public class Main {
    static int MAX = 0;

    public static void main(String[] args) {
        System.out.println("My name");
        System.out.print("Enter N: ");

        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();
        Integer matrix[][] = new Integer[N][N];
        Initialization(matrix);
        Search(matrix);
    }


    static void Initialization(Integer[][] matrix) {
        Random r = new Random();
        System.out.println("Matrix before processing");
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix.length; j++) {
                matrix[i][j] = r.nextInt(100);
                System.out.print(matrix[i][j] + "\t");
            }
            System.out.print("\n");
        }
    }
    static void Search(Integer matrix[][]) {
        int max = 0;

        for(int i = 0; i < matrix.length; i++) {
            for(int j = 0; j < matrix.length; j++) {
                if (matrix[i][j] > max) {
                    max = matrix[i][j];
                }
            }
        }
        MAX = max;
        System.out.println("Max element in matrix: " + max);
    }
}

Answer 1

正如@idanz 在评论中指出的那样，您不能重新定义数组大小或矩阵，因为它只是一个数组数组。

你可以做的是实例化一个比原始矩阵少一行的新数组（或在本例中为新矩阵）。在您的搜索方法中，您可以 return 要“删除”的行的索引，然后使用此索引将原始矩阵中的每个元素复制到新矩阵中，但要“删除”的行中的元素除外，即请勿复制。

附带说明一下，我还注意到您不正确地迭代了矩阵的元素。您最内层的循环应该检查 matrix[i].length 的长度，而不是 matrix.length。此外，我还调整了一些变量和方法名称，因为它们不符合 naming conventions。您的变量和方法应以小写字母开头，并以 camel-case 表示法编写。

public class Main {

    public static void main(String[] args) {
        System.out.print("Enter N: ");
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();

        //Initializing and printing the matrix
        Integer matrix[][] = new Integer[n][n];
        initialization(matrix);
        print(matrix);

        //Retrieving the index row with the maximum element
        int rowWithMax = search(matrix);

        //Retrieving a new a matrix without the row to delete and assigning it to the old matrix
        matrix = deleteRow(matrix, rowWithMax);

        System.out.println("\nNew matrix without the deleted row");
        print(matrix);
    }


    static void print(Integer[][] matrix) {
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[i].length; j++) {
                System.out.print(matrix[i][j] + "\t");
            }
            System.out.println();
        }
    }

    static void initialization(Integer[][] matrix) {
        Random r = new Random();
        System.out.println("Matrix before processing");
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[i].length; j++) {
                matrix[i][j] = r.nextInt(100);
            }
        }
    }

    static int search(Integer matrix[][]) {
        int max = 0, rowWithMax = -1;

        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[i].length; j++) {
                if (matrix[i][j] > max) {
                    max = matrix[i][j];
                    rowWithMax = i;
                }
            }
        }
        System.out.println("\nMax element in matrix: " + max);
        return rowWithMax;
    }

    static Integer[][] deleteRow(Integer matrix[][], int rowToDelete) {
        //Since in Java you cannot redefine the size of an array (in this case an array of array of int)
        //you need to instantiate a new matrix filled with the elements of the original matrix except
        //for the row with the highest element.

        //If no row must be deleted (i.e. no proper index has been passed) then the original matrix is simply returned
        if (rowToDelete < 0) {
            return matrix;
        }

        Integer[][] matrix2 = new Integer[matrix.length - 1][matrix.length];
        int displacedIndex;
        for (int i = 0; i < matrix.length; i++) {
            //Skipping the row to delete (i.e. the row which must not be copied within the new matrix)
            if (i != rowToDelete) {
                //Since i is the row index of the original matrix, this can't be the same index for the new matrix after skipping the row to delete,
                //so, we need to create a displaced index for the new matrix which corresponds to i before meeting the deleted row while to i-1 after
                //meeting the deleted row
                displacedIndex = i < rowToDelete ? i : i - 1;

                for (int j = 0; j < matrix[i].length; j++) {
                    matrix2[displacedIndex][j] = matrix[i][j];
                }
            }
        }

        return matrix2;
    }
}

找到矩阵的最大元素并删除具有该元素的行

Find the maximum element of the matrix and delete a row with this element

java

matrix