using System.Collections; public class Node : Element { public Node(string name) { Name = name; } public string Name { get; } public override bool Equals(object? obj) { if (obj == null || GetType() != obj.GetType()) return false; return ((Node)obj).Name == Name; } public override int GetHashCode() => Name.GetHashCode(); } public class Edge : Element { public Edge(string node1, string node2) { Node1 = node1; Node2 = node2; } public string Node1 { get; } public string Node2 { get; } public override bool Equals(object? obj) { if (obj == null || GetType() != obj.GetType()) return false; return ((Edge)obj).Node1 == Node1 && ((Edge)obj).Node2 == Node2; } public override int GetHashCode() => Node1.GetHashCode() ^ Node2.GetHashCode(); } public class Attr { public Attr(string key, string value) { Key = key; Value = value; } public string Key { get; } public string Value { get; } public override bool Equals(object? obj) { if (obj == null || GetType() != obj.GetType()) return false; return ((Attr)obj).Key == Key && ((Attr)obj).Value == Value; } public override int GetHashCode() => Key.GetHashCode() ^ Value.GetHashCode(); } public class Graph : Element { private List nodes = new List(); private List edges = new List(); public IEnumerable Nodes => nodes; public IEnumerable Edges => edges; public IEnumerable Attrs => attrs; public void Add(Node node) => nodes.Add(node); public void Add(Edge edge) => edges.Add(edge); } public abstract class Element : IEnumerable { protected List attrs = new List(); public void Add(string key, string value) => attrs.Add(new Attr(key, value)); public IEnumerator GetEnumerator() => attrs.GetEnumerator(); IEnumerator IEnumerable.GetEnumerator() => GetEnumerator(); }