问题
I want to check if Object with given values exists in SortedSet<>
but I don't understand how custom comparation works here. In List<>.Exists()
i could just use lambda, but I cannot do that there and i don't get that whole interface thing while msdn says i need to override int
returning function.
public class Node
{
public int X, Y;
public int rand;
public Node(int x, int y, int r)
{ X = x; Y = y; rand = r; }
}
class Program
{
static void Main(string[] args)
{
SortedSet<Node> mySet = new SortedSet<Node>();
mySet.Add(new Node(1, 2, 90));
Node myNode = new Node(1, 2, 50);
// I want this to check if X and Y are the same
if (mySet.Contains(myNode, interfaceThing))
Console.WriteLine("Sth is already on that (X, Y) position");
}
}
Is there any simple way to do that?
回答1:
You have two options, create a class that implements IComparer<Node>
(you should do IEqualityComparer<Node>
too) and pass that in to the constructor of the sorted set.
public class NodeComparer : IComparer<Node>, IEqualityComparer<Node>
{
public int Compare(Node node1, Node node2)
{
//Sorts by X then by Y
//perform the X comparison
var result = node1.X.CompareTo(node2.X);
if (result != 0)
return result;
//Perform the Y Comparison
return node1.Y.CompareTo(node2.Y);
}
public bool Equals(Node x, Node y)
{
if (ReferenceEquals(x, y)) return true;
if (ReferenceEquals(x, null)) return false;
if (ReferenceEquals(y, null)) return false;
if (x.GetType() != y.GetType()) return false;
return x.X == y.X && x.Y == y.Y && x.rand == y.rand;
}
public int GetHashCode(Node obj)
{
unchecked
{
var hashCode = obj.X;
hashCode = (hashCode * 397) ^ obj.Y;
hashCode = (hashCode * 397) ^ obj.rand;
return hashCode;
}
}
}
public class Node
{
public int X, Y;
public int rand;
public Node(int x, int y, int r)
{ X = x; Y = y; rand = r; }
}
class Program
{
static void Main(string[] args)
{
SortedSet<Node> mySet = new SortedSet<Node>(new NodeComparer());
mySet.Add(new Node(1, 2, 90));
Node myNode = new Node(1, 2, 50);
// I want this to check if X and Y are the same
if (mySet.Contains(myNode, interfaceThing))
Console.WriteLine("Sth is already on that (X, Y) position");
}
}
Or have Node implement the relevant methods it needs itself.
public class Node : IEquatable<Node>, IComparable<Node>
{
public int X, Y;
public int rand;
public Node(int x, int y, int r)
{ X = x; Y = y; rand = r; }
public bool Equals(Node other)
{
if (ReferenceEquals(null, other)) return false;
if (ReferenceEquals(this, other)) return true;
return X == other.X && Y == other.Y && rand == other.rand;
}
public override bool Equals(object obj)
{
if (ReferenceEquals(null, obj)) return false;
if (ReferenceEquals(this, obj)) return true;
if (obj.GetType() != this.GetType()) return false;
return Equals((Node)obj);
}
public override int GetHashCode()
{
unchecked
{
var hashCode = X;
hashCode = (hashCode*397) ^ Y;
hashCode = (hashCode*397) ^ rand;
return hashCode;
}
}
public int CompareTo(Node other)
{
//First order by X then order by Y then order by rand
var result = X.CompareTo(other.X);
if (result != 0)
return result;
result = Y.CompareTo(other.Y);
if (result != 0)
return result;
return rand.CompareTo(other.rand);
}
}
回答2:
A simple dirty way to do this is with some linq
if(myNode.Where(n => n.X == myNode.X && n.Y == myNode.Y).Count > 0)
You could also do this in an extension method to be able to call this more than once
public static class Extensions
{
public static bool ContainsNode(this IList<Node> nodes, Node value)
{
return nodes.Where(n => n.X == value.X && n.Y == value.Y).Count > 0;
}
}
Although if you want to be more efficient, you should use a simple foreach loop instead, to possibly shortcut iterating through the whole list once one is found.
Edit: totally forgot about .Any()
bassically does the Where for you but does cut out early.
public static class Extensions
{
public static bool ContainsNode(this IList<Node> nodes, Node value)
{
return nodes.Any(n => n.X == value.X && n.Y == value.Y).Count > 0;
}
}
来源:https://stackoverflow.com/questions/22696329/sortedset-contains-how-to-implement-own-comparation