The value assignment in  first circle  (the significant part of the recursion)

The results of it:

 

the codes：

#include <iostream>
using namespace std;
int main()
{
    int a[7][7];
    int count_num = 0;
    int n = 7, layer = 0;
    int row, column;
    for(column = 0; column <n; ++column){
        a[layer][column] = ++count_num;
    }
    for(row = 1; row<n; ++row){
        a[row][column-1] = ++count_num;
    }
    for(column = n-2; column >=0; --column){
        a[row-1][column] = ++count_num;
    }
    for(row = n-2; row > 0 ; --row){
        a[row][column+1] = ++count_num;
    }
    return 0;
}

// create a spiral matrix using positive integer and output it
#include <iostream>
using namespace std;
void create_spiral_matrix(int(*a)[50], int n, int layer);
void dis_spiral_matrix(int(*a)[50] , int n);
int main()
{
    int a[50][50];
    cout << "Input an integer number range from 1 to 50 and if you would like to end this program, you could input 0:" << endl;
    int n;
    cin >> n;
    //int a[n][n];
    create_spiral_matrix(a , n, 0);
    dis_spiral_matrix(a, n);
    return 0;
}
int count_num = 0;
void create_spiral_matrix(int(*a)[50], int n, int layer)
{
    if(n<=0){
        return ;
    }
    int row, column;
    for(column = layer; column < n+layer; ++column){
        a[layer][column] = ++count_num;
    }
    for(row = layer + 1; row < n+layer; ++row){
        a[row][column-1] = ++count_num;
    }
    for(column -= 2; column >=layer; --column){
        a[row-1][column] = ++count_num;
    }
    for(row -= 2; row > layer ; --row){
        a[row][column+1] = ++count_num;
    }
    create_spiral_matrix(a, n-2, layer+1);
}
void dis_spiral_matrix(int(*a)[50] , int n)
{
    int i , j;
    for(i=0; i<n; ++i){
        for(j=0; j<n; ++j){
            cout << a[i][j] << ' ';
        }
        cout << endl;
    }
}