Task

Produce a spiral array.



A   spiral array   is a square arrangement of the first    N2   natural numbers,   where the

numbers increase sequentially as you go around the edges of the array spiraling inwards.



For example, given   5,   produce this array:

 0  1  2  3  4
15 16 17 18  5
14 23 24 19  6
13 22 21 20  7
12 11 10  9  8



Related tasks

   Zig-zag matrix 
   Identity_matrix
   Ulam_spiral_(for_primes)


public int[,] Spiral(int n) {
    int[,] result = new int[n, n];
 
    int pos = 0;
    int count = n;
    int value = -n;
    int sum = -1;
 
    do {
        value = -1 * value / n;
        for (int i = 0; i < count; i++) {
            sum += value;
            result[sum / n, sum % n] = pos++;
        }
        value *= n;
        count--;
        for (int i = 0; i < count; i++) {
            sum += value;
            result[sum / n, sum % n] = pos++;
        }
    } while (count > 0);
 
    return result;
}
 
 
// Method to print arrays, pads numbers so they line up in columns
public void PrintArray(int[,] array) {
    int n = (array.GetLength(0) * array.GetLength(1) - 1).ToString().Length + 1;
 
    for (int i = 0; i < array.GetLength(0); i++) {
        for (int j = 0; j < array.GetLength(1); j++) {
            Console.Write(array[i, j].ToString().PadLeft(n, ' '));
        }
        Console.WriteLine();
    }
}