9. Заполнение по спирали.

#include <iostream>
using namespace std;
int main()
{
    int a[500][500];
    int n, x, y, c = 0, t = 0, q = -1;
    cin >> n;
    x = n;
    y = n;
    a[n][n] = c;
    while (x != -1) {
        for (int i = 0 ; i <= t; i++) {
            c++;
            x += q;
            if (x != -1) {
                a[x][y] = c;
            }
        }
        for (int i = 0 ; i <= t; i++) {
            c++;
            y += q;
            if (x != -1) {
                a[x][y] = c;
            }
        }
        q = -q;
        t++;
    }
    for (int i = 0; i < 2*n + 1; i++) {
        for (int j = 0; j < 2*n +1; j++) {
            if (a[i][j] < 10) {
                cout << "  ";
            }
            else {
                if (a[i][j] < 100) {
                    cout << " ";
                }
            }
            cout << a[i][j];
        }
        cout << endl;
    }
}