Print matrix spiral

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);
 }
}