Initialise an array in spiral form (inside out).

/*

Initialise the center element of the matrix with 1 and then assign all other cells in spiral order.
21 22 23 24 25
26  7   8   9  10
19  6   1   2  11
18  5   4   3  12
17 16 15 14 13

*/

// this will work only for odd number of rows and columns square matrix as in even rows and columns square //matrix there is no center element.

#include<iostream.h>

#include<conio.h>

const int rowcol=5;

int matrix[rowcol][rowcol];

void spiralinvert(int row,int col)

{

     int count=2;

     int cstart=col/2,cend=cstart+1;

     int rstart=row/2,rend=rstart+1;

     int n=row*col;

     matrix[cstart][rstart]=1;

     cout<<"spiral starts"<<endl;

     while(1)

     {

                   

                   for(int i=cstart+1;i<=cend;i++,count++)

                           matrix[rstart][i]=count;

                   cstart--;

                   if(count>=n)

                               break;

                   for(int j=rstart+1;j<=rend;j++,count++)

                                   matrix[j][cend]=count;

                   rstart--;

                   if(count>=n)

                               break;

                   for(int k=cend-1;k>=cstart;k--,count++)

                           matrix[rend][k]=count;

                   cend++;

                   if(count>=n)

                      break;

                   for(int l=rend-1;l>=rstart;l--,count++)

                           matrix[l][cstart]=count;

                   rend++;

                   if(count>=n)

                            break;

     }

     cout<<"spiral ends"<<endl;

}

void display(int row,int col)

{

     for(int i=0;i<row;i++)

     {

             cout<<"\n";

             for(int j=0;j<col;j++)

                     cout<<"\t"<<matrix[i][j];

     }

}

int main()

{

    spiralinvert(rowcol,rowcol);

    display(rowcol,rowcol);

    getch();

    return 0;

}