Question

How to append boundary elements of a matrix to an array in Java

Answer 1

import java.util.Arrays;

public class MyClass {
    private static int GetBoundariesLength(int matrix[][]) {
        int rows = matrix.length;
        int cols = matrix[0].length;
         
        return (rows * 2) + (cols * 2) - 4;
    }
    private static void AppendMatrixBoundariesToArray(int[][] matrix, Integer[] array) {
        int rows = matrix.length;
        int cols = matrix[0].length;
     
        int array_index = 0;
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                if (i == 0 || j == 0 || i == rows - 1 || j == cols - 1) {
                    array[array_index++] = matrix[i][j];
                }
            }
        }
    }

    public static void main(String args[]) {
        int matrix[][] = { 
	        { 1,  2,  3,  4,  5},
            { 6,  7,  8,  9, 10},
            {11, 12, 13, 14, 15},
            {16, 17, 18, 19, 20} 
	    };
	    
	    Integer[] array = new Integer[GetBoundariesLength(matrix)]; 
	    
	    AppendMatrixBoundariesToArray(matrix, array);

	    System.out.println(Arrays.toString(array));
    }
}






/*
run:

[1, 2, 3, 4, 5, 6, 10, 11, 15, 16, 17, 18, 19, 20]
      
*/

 

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