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Data Structures

## Print a given matrix in spiral form

Given a 2D array, print it in spiral form. See the following examples.


Input:

1    2   3   4

5    6   7   8

9   10  11  12

13  14  15  16

Output:

1 2 3 4 8 12 16 15 14 13 9 5 6 7 11 10

Input:

1   2   3   4  5   6

7   8   9  10  11  12

13  14  15 16  17  18

Output:

1 2 3 4 5 6 12 18 17 16 15 14 13 7 8 9 10 11



Solution:

#include <stdio.h>
#define R 3
#define C 6

void spiralPrint(int m, int n, int a[R][C])
{
int i, k = 0, l = 0;

/*  k - starting row index
m - ending row index
l - starting column index
n - ending column index
i - iterator
*/

while (k < m && l < n)
{
/* Print the first row from the remaining rows */
for (i = l; i < n; ++i)
{
printf("%d ", a[k][i]);
}
k++;

/* Print the last column from the remaining columns */
for (i = k; i < m; ++i)
{
printf("%d ", a[i][n-1]);
}
n--;

/* Print the last row from the remaining rows */
if ( k < m)
{
for (i = n-1; i >= l; --i)
{
printf("%d ", a[m-1][i]);
}
m--;
}

/* Print the first column from the remaining columns */
if (l < n)
{
for (i = m-1; i >= k; --i)
{
printf("%d ", a[i][l]);
}
l++;
}
}
}

/* Driver program to test above functions */
int main()
{
int a[R][C] = { {1,  2,  3,  4,  5,  6},
{7,  8,  9,  10, 11, 12},
{13, 14, 15, 16, 17, 18}
};

spiralPrint(R, C, a);
return 0;
}


OUTPUT:

1 2 3 4 5 6 12 18 17 16 15 14 13 7 8 9 10 11

Time Complexity:
Time complexity of the above solution is O(mn).