假设列大小相同，如何在Java中附加和预启用2D数组，而无需数组复制

Question

我尝试关注此一个，您如何正确地将两个2D数组在Java中正确地附加？删除所有阵列的配置，但出了点问题。我还尝试了另一个指南，但这只有在行相同的情况下才起作用。

public int [][] appendMatrix(int[][]matrix, int [][] matrix2)
    {
        this.matrix = new int[matrix.length + matrix2.length][matrix[0].length];
        for(int i = 0; i < matrix.length; i++)
        {
            for(int j = 0; j < matrix[i].length; j++)
            {
                this.matrix[i][j] = matrix[i][j];
            }
            for(int j = matrix.length; j < matrix.length + matrix2.length; j++)
            {
                this.matrix[i][j]= matrix2[i-matrix.length][j];
            }   
        }
        return this.matrix;**

Answer 1

要考虑的重要事情是，当我们从第一个矩阵中的最后一行走时，我们要保留该值我们与最终矩阵的第二个矩阵，不会丢失轨道。

示例输出：输出作为数组，可视化为矩阵

package matrix;
// I know you don't want to use imports, this is simply for testing purposes.
import java.util.Arrays;
public class MatrixAddition
{
    public static void main(String[] args)
    {
        int[][] matrix1 =
        {
                { 1, 2, 3 },
                { 4, 5, 6 },
                { 7, 8, 9 },
                { 10, 11, 12 } };
        int[][] matrix2 =
        {
                { 1, 1, 1 },
                { 2, 3, 4 } };

        System.out.println("Appending the two matrices results in: ");
        System.out.println(Arrays.deepToString(twoDMatrixAppend(matrix1, matrix2)));
        printMatrix(twoDMatrixAppend(matrix1, matrix2));
        System.out.println("nPrepending the two matrices results in: ");
        System.out.println(Arrays.deepToString(twoDMatrixPrepend(matrix1, matrix2)));
        printMatrix(twoDMatrixPrepend(matrix1, matrix2));
    }

    private static int[][] twoDMatrixAppend(int[][] matrix1, int[][] matrix2)
    {
        if (matrix1[0].length != matrix2[0].length)
        {
            return null; // Or throw new incompatible matrices exception
        }
        int resultingRowLength = matrix1.length + matrix2.length; // The new length of the resulting matrix
        int[][] result = new int[resultingRowLength][matrix1[0].length];
        int currentRow, col, matrixTwoRowStart;
        for (currentRow = 0; currentRow < matrix1.length; currentRow++)
        {
            for (col = 0; col < matrix1[0].length; col++)
            {
                result[currentRow][col] = matrix1[currentRow][col];
            }
        }
        for (matrixTwoRowStart = 0; matrixTwoRowStart < matrix2.length; matrixTwoRowStart++, currentRow++)
        {
            for (col = 0; col < matrix2[0].length; col++)
            {
                result[currentRow][col] = matrix2[matrixTwoRowStart][col];
            }
        }
        return result;
    }
    private static int[][] twoDMatrixPrepend(int[][] matrix1, int[][] matrix2)
    {
        return twoDMatrixAppend(matrix2, matrix1);
    }
    private static void printMatrix(int[][] arr)
    {
        System.out.println();
        int row, col;
        for (row = 0; row < arr.length; row++)
        {
            for (col = 0; col < arr[0].length; col++)
            {
                System.out.print(String.format("%4d", arr[row][col]));
            }
            System.out.println();
        }
    }
}