Grupy krwi - operacje bitowe

#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

bool qualifies(int donor_idx, int recipient_idx)
{
    return (~(donor_idx & ~recipient_idx) & 7) == 7;
}

int main()
{
    const size_t count = 8;
    string types[count] = { "0-", "0+", "B-", "B+", "A-", "A+", "AB-", "AB+" };

    string donor;
    cout << "Dawca: ";
    cin >> donor;

    size_t donor_idx = find(types, types + count, donor) - types;
    if(donor_idx >= count)
        cout << "Nie ma takiej grupy";
    else
    {
        cout << "Biorcy:";

        for(int recipient_idx = 0; recipient_idx < count; recipient_idx++)
            if(qualifies(donor_idx, recipient_idx))
                cout << "\n" << types[recipient_idx];
    }

    cout << "\n";
}

size_t donor_idx = count - distance(find(types, types + count, donor), types + count);

Czemu tak zrobiłeś?

qualifies wg mnie powinno zwracać
```cpp
return recipient_idx|donor_idx==recipient_idx;

#include <iomanip>
#include <iostream>
using namespace std;
 
int main()
  {
   const char *types[]={"0Rh-", "0Rh+", "BRh-", "BRh+", "ARh-", "ARh+", "ABRh-", "ABRh+" };
   const size_t count=sizeof(types)/sizeof(*types);
   cout<<setw(6)<<"D.\B.";
   for(size_t x=0;x<count;++x) cout<<setw(6)<<types[x];
   cout<<endl;
   for(size_t y=count-1;y<count;--y)
     {
      cout<<setw(6)<<types[y];
      for(size_t x=0;x<count;++x)
        {
         cout<<setw(3)<<(((y|x)==y)?'X':' ')<<"   ";
        }
      cout<<endl;
     }
   return 0;
  }