Spiral matrix in C

A spiral matrix is a matrix of the type which puts numbers in a circular fashion rather than in row-major or column-major fashion.

 

This is the spiral matrix in which one has stored value in clockwise and other one in anticlockwise:

******************************Source code**********************************

#include <stdio.h>

#define UP 1

#define DOWN 2

#define LEFT 3

#define RIGHT 4

#define MAX 6

void main()

{

int initial_direction = UP , n = MAX , p = 1 ;

// intial_direction is set to UP because we need to start moving right

int r ,c , a[MAX][MAX];

int row_right = 0 , column_down = n-1 , row_left = n-1 , column_up = 0 ;

//Set all elements of the matrix to 0

for(r = 0 ; r < MAX ; r++)

{

for(c = 0 ; c < MAX ; c++)

a[r][c] = 0 ;

}

//Generate elements of the spiral matrix

while(p != n*n+1)

{

if(initial_direction == UP)

{

//Move RIGHT

r = row_right++ ;

for(c = 0 ; c < n ; c++)

{

if(a[r][c] == 0)

a[r][c] = p++;

}

initial_direction = RIGHT ;

}

else if(initial_direction == RIGHT)

{

//Move down

c = column_down-- ;

for(r = 0 ; r < n ; r++)

{

if(a[r][c] == 0)

a[r][c] = p++;

}

initial_direction = DOWN ;

}

else if(initial_direction == DOWN)

{

//Move left

r = row_left-- ;

for(c = n-1 ; c >= 0 ; c--)

{

if(a[r][c] == 0)

a[r][c] = p++;

}

initial_direction = LEFT ;

}

else if(initial_direction == LEFT)

{

//Move up

c = column_up++;

for(r = n-1 ; r >= 0 ; r--)

{

if(a[r][c] == 0)

a[r][c] = p++;

}

initial_direction = UP ;

}

}

//Print the matrix

printf("\n\n");

for(r = 0 ; r < MAX ; r++)

{

for(c = 0 ; c < MAX ; c++)

printf("%4d ",a[r][c]);

printf("\n");

}

}

********************************Output**********************************