I solved it :
#include
using namespace std;
int main()
{
int a, b, c, d, i, j, k, m , n,o,g,z,x ;
char st = ‘*’, dt = ‘.’, t;
cin >> a;
for (i = 0; i < a; i++)
{
cin >> b >> c>>m ;
c%2==0 ? k=0:k=m+1 ;
n=4+(m-1)*2 ;
b=(m+1)*b+1; c=(m+1)*c+1 ;
for (d = 1; d <=b; d++)
{
for (j = 1,z=c; j <= c ; j++,z--)
{
if (d%(m+1)==1)
{
cout<<st ; }
else
{
if (j%(m+1)==1)
{
cout<<st ;
}
else {
if(j%n==d%n) cout<<"\\" ;
else if(z%n==(d+k)%n)cout<<"/" ;
else cout<<dt ;
}
}
}cout<<endl ;
}cout<<endl ;
}
}