对包含引用类型的结构的哈希集相等替代

Question

I am trying to implement struct containing state of a board game, so I need multiple states of a game in a HashSet.

Data part looks like this:

struct Sokoban
{

    public List<List<char>> data;   // data matrix
    public int sx, sy;              // sokoban's position
    public int bx, by;              // box position
    public int cx, cy;              // final box position

As struct are value types, when I create new instance with:

Sokoban nextState = actualState; 

where actualState is a formerly initialized instance, it should copy all fields of actualState to nextState . So nextState and actualState now points to the same List>. . My question is, how can have a proper copy of this struct? If I create a constructor like:

public Sokoban(Sokoban originalSokoban)          
    {

        this.sx = originalSokoban.sx;
        this.sy = originalSokoban.sy;
        this.bx = originalSokoban.bx;
        this.by = originalSokoban.by;
        this.cx = originalSokoban.cx;
        this.cy = originalSokoban.cy;


        List<List<char>> data2 = new List<List<char>>();

        for (int i = 0; i < originalSokoban.data.Count(); i++)
        {

            data2.Add( new List<char>(originalSokoban.data[i]));
        }
        this.data = data2;
     }

it works. But, when I add these two distinct instances to hashset they are not recognized as same. This is my code for overriden GetHashCode,Equals, ==, != operators :

    public override int GetHashCode()
    {
        return (( sx+sy+bx+by+ cx+ cy).GetHashCode()+(data).GetHashCode());
    }          

    public static bool operator ==(Sokoban x, Sokoban y)
    {
        bool isEqual = true;
        for (int i = 0; i < x.data.Count(); i++)
        {
            for (int j = 0; j < x.data[0].Count(); j++)
            {
                if (x.data[i][j] != y.data[i][j])
                {
                    isEqual = false;
                }
            }
        }

        return isEqual &&
        x.sx == y.sx &&
        x.sy == y.sy &&
        x.bx == y.bx &&
        x.by == y.by &&
        x.cx == y.cx &&
        x.cy == y.cy;
    }

    public static bool operator !=(Sokoban x, Sokoban y)
    {
        return !(x == y);
    }

    public override bool Equals(object obj)
    {
         return obj is Sokoban && this == (Sokoban)obj;       
    }      

I don't know where I'm making mistake, if you have any comments or remarks I'll gladly accept any help, I'm stuck with this for 3 days, thank you :)

Answer 1

Looking on the code, most likely the problem is here

 public override int GetHashCode()
 {
   //(data).GetHashCode() !!! List<T>::GetHashCode()..
   return (( sx+sy+bx+by+ cx+ cy).GetHashCode()+(data).GetHashCode());
 }    

data.GetHashCode() is unique for every new instance of the struct, so your resulting GetHashCode() may result in totally different number for instances that are supposed to be equal according to your logic. Change your GetHashCode() method to meet your needs.