Hexa.cpp

/*

Pattern challenge
Author A.S.

        @ @ @ @ @ @ @ @
       @ @   @   @   @ @
      @   @ @     @ @   @
     @ @ @ @       @ @ @ @
    @       @ @ @ @       @
   @ @     @ @   @ @     @ @
  @   @   @   @ @   @   @   @
 @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
  @   @   @   @ @   @   @   @
   @ @     @ @   @ @     @ @
    @       @ @ @ @       @
     @ @ @ @       @ @ @ @
      @   @ @     @ @   @
       @ @   @   @   @ @
        @ @ @ @ @ @ @ @

*/

#include<stdlib.h>     // abs
#include<iomanip>
#include<iostream>
using   std::setw,
        std::cout, std::endl;

auto main()
    -> int
{
    const int n = 3;
    const int w = 1 << n;
    for( int y = 0; y < 2*w - 1; ++y ) {
        const int cw = w - 1;
        cout << setw( abs( cw - y ) ) << "";
        const int cy = cw - abs( cw - y );
        for( int x = 0; x < w + y; ++x ) {
            const int tx = (x < cy? x : x < w? w - 1 - x : x + 1 - w);
            const int ty = (x < cy? cy : x < w? w - 1 - cy : cy);
            const char ch = (tx & ~ty? ' ' : '@');
            cout << setw( 2 ) << ch;
        }
         cout << endl;
    }
}