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Printing array in spiral order is not that tough as we think, if we properly maintain directions and positions of indexes
we are done, here is such simple program…

/*Printing array spirally for ex.

1    2    3    4

5    6    7    8

9    10   11  12

13   14   15   16

need to print the above matrix in 1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11, 10 order (i.e. spirally) */

 
#include <stdio.h>
 
#define MAX_COLS 20
 
enum
{
  ARR_RIGHT,
  ARR_DOWN,
  ARR_LEFT,
  ARR_UP
};
 
int array_spiral_print(int arr[][MAX_COLS], int num_rows, int num_cols)
{
  int m = num_rows-1;  //num_rows
  int n = num_cols-1;  //num cols
  int m_begin = 0, n_begin = 0, m_end = m, n_end = n;
  int direction = ARR_RIGHT;
  int i,j;
 
  while((m_begin<m) && (m_end>0) && (n_begin<n) && (n_end>0))
  {
    switch(direction)
    {
    case ARR_RIGHT:
      for (j=n_begin; j<=n_end; j++)
      {
        printf("%d ", arr[m_begin][j]);
      }
      m_begin++;
      direction = ARR_DOWN;
      break;
    case ARR_DOWN:
      for (i=m_begin; i<=m_end; i++)
      {
        printf("%d ", arr[i][n_end]);
      }
      n_end- -;
      direction = ARR_LEFT;
      break;
    case ARR_LEFT:
      for (j=n_end; j>=n_begin; j- -)
      {
        printf("%d ", arr[m_end][j]);
      }
      m_end- -;
      direction = ARR_UP;
      break;
    case ARR_UP:
      for (i=m_end; i>=m_begin; i- -)
      {
        printf("%d ", arr[i][n_begin]);
      }
      n_begin++;
      direction = ARR_RIGHT;
 
      break;
    }
  }
 
  return 0;
}
 
#ifdef TEST
int main()
{
  int arr[][MAX_COLS] = {{1, 2, 3, 10}, {4, 5, 6, 11}, {7, 8, 9, 12}, {13, 14, 15, 16}};
  array_spiral_print(arr, 4, 4);
}
#endif

download [source code] for the above program which is a c file.

please let me know your comments….

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Related Blog Items

• Printing array spirally - recursive routine
• Print In Reverse-Order
• Questions asked in various job interviews (in Programming)
• Printing linked List in Reverse without Reversing The List Actually
• Max Sum between two array indexes

This entry was written by ponnada and posted on February 16, 2007 at 8:10 pm and filed under Algorithms, C Tidbits. Bookmark the permalink. Follow any comments here with the RSS feed for this post. Post a comment or leave a trackback: Trackback URL.