Liet ke so xoan oc - KO DUNG MANG

#include<conio.h>
#include<stdio.h>
int n;
int class_(int x, int y)
{
    int m=x-1;
    if (y-1<m) m=y-1;
    if (n-x<m) m=n-x;
    if (n-y<m) m=n-y;
    return m+1;
}
int first(int c)
{
    int i,t=1,n1=n;
    for (i=1;i<=c-1;i++)
    {
        t=t+(n1-1)*4;
        n1=n1-2;
    }
    return t;
}
int gt(int x, int y)
{
    int c,n1,i0,j0,i,j,k=0;
    c=class_(x,y);
    n1=n-2*(c-1);
    i0=x-c+1; j0=y-c+1;
    i=1;
    for (j=1;j<=n1;j++)
        if (i==i0 && j==j0) return k+first(c);
        else k++;
    j--;
    for (i=2;i<=n1;i++)
        if (i==i0 && j==j0) return k+first(c);
        else k++;
    i--;
    for (j--;j>=1;j--)
        if (i==i0 && j==j0) return k+first(c);
        else k++;
    j++;
    for (i--;i>=1;i--)
        if (i==i0 && j==j0) return k+first(c);
        else k++;
    i++;
}
int main()
{
    int i,j;
    printf("Nhap vao so n= "); scanf("%d",&n);
    for (i=1;i<=n;i++)
    {
        for (j=1;j<=n;j++)
            printf("%3d ",gt(i,j));
        printf("\n");
    }
    getch();
    return 0;
}