Question

How to print the boundary elements of a matrix in Java

Answer 1

public class MyClass {
    private static void printMatrixBoundaries(int[][] matrix) {
        int rows = matrix.length;
        int cols = matrix[0].length;
    
    	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)	{
    				System.out.print(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} 
	    };

	    printMatrixBoundaries(matrix);
    }
}






/*
run:
      
1 2 3 4 5 6 10 11 15 16 17 18 19 20 
      
*/

 

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Answer 2

public class MyClass {
    private static void printMatrixBoundaries(int[][] matrix) {
        int rows = matrix.length;
        int cols = matrix[0].length;
    
    	for (int j = 0; j < cols; j++) {
            System.out.print(matrix[0][j] + " ");
        }
         
        for (int j = 0; j < cols; j++) {
            if (j == cols - 1) {
                for (int i = 1; i < rows; i++) {
                    System.out.print(matrix[i][j] + " ");
                }
            }
        }
         
        for (int j = cols - 2; j > -1; j--) {
            System.out.print(matrix[rows - 1][j] + " ");
        }
         
        for (int i = rows - 2; i > 0; i--) {
            System.out.print(matrix[i][0] + " ");
        }
    }
    
    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} 
	    };

	    printMatrixBoundaries(matrix);
    }
}






/*
run:
      
1 2 3 4 5 10 15 20 19 18 17 16 11 6 
      
*/

 

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