Problem

Print a matrix in spiral fashion.

Solution

We will first print the periphery of the matrix by the help of 4 for loops. Then recursively call this function to do the same thing with inner concentric rectangles. We will pass this information by a variable named depth, which will tell how many layers from outside should be ignored.

Code

public class PrintMatrixSpiral{ public static void main(String[] args) {  int[][] matrix =  {  { 3, 4, 5, 6, 2, 5 },  { 2, 4, 6, 2, 5, 7 },  { 2, 5, 7, 8, 9, 3 },  { 2, 4, 7, 3, 5, 8 },  { 6, 4, 7, 3, 5, 7 } };  printSpiral(matrix); } public static void printSpiral(int[][] matrix) {  printSpiral(matrix, 0); } private static void printSpiral(int[][] matrix, int depth) {  if (matrix == null && matrix.length == 0)   return;  int rows = matrix.length;  int cols = matrix[0].length;  if (2 * depth > Math.min(rows, cols))   return;  for (int i = depth; i < cols - depth - 1; ++i)  {   System.out.print(matrix[depth][i] + ",");  }  for (int i = depth; i < rows - depth - 1; ++i)  {   System.out.print(matrix[i][cols - depth - 1] + ",");  }  for (int i = rows - depth; i > depth; --i)  {   System.out.print(matrix[rows - depth - 1][i] + ",");  }  for (int i = rows - depth - 1; i > depth; --i)  {   System.out.print(matrix[i][depth] + ",");  }  printSpiral(matrix, ++depth); }}