My source code

#include<iostream>
using namespace std;
main (){

    int b,x,y,z;

    cout<<"Masukkan Batas : ";
    cin>>b;
    cout<<endl;


    for (y=1;y<=b-1;y++){

        for (z=y;z<=b;z++) {
            cout<<"  ";
        }
        for (x=1;x<=y-1;x++){
            if (x==1)
                cout<<" *";
            else
                cout<<"  ";
        }
        for (x=y;x>=1;x--) {
            if (x==1)
                cout<<" *";
            else
                cout<<"  ";
        }
        cout<<endl;
    }

    for (y=b;y>=1;y--){

        for (z=y;z<=b;z++) {
            cout<<"  ";
        }
        for (x=1;x<=y-1;x++){
            if (x==1)
                cout<<" *";
            else
                cout<<"  ";
        }
        for (x=y;x>=1;x--) {
            if (x==1 or x==b)
                cout<<" *";
            else
                cout<<"  ";
        }
        cout<<endl;
    }

}