十六、C# 常用集合类及构建自定义集合(使用迭代器)

 1     class Program
 2     {
 3         static void Main(string[] args)
 4         {
 5             CSharpPrimitiveTypes primitives = new CSharpPrimitiveTypes();
 6             foreach (string primitive in primitives)
 7             {
 8                 Console.WriteLine(primitive);
 9             }
10  
11             Console.ReadLine();
12  
13  
14         }
15  
16  
17     }
18  
19     public class CSharpPrimitiveTypes : IEnumerable<string>
20     {
21         public IEnumerator<string> GetEnumerator()
22         {
23             yield return "object";
24             yield return "byte";
25             yield return "uint";
26             yield return "ulong";
27             yield return "float";
28             yield return "char";
29             yield return "bool";
30             yield return "string";
31         }
32  
33         //因为System.Collections.Generic.IEnumerable<T>继承
34         //System.Collections.IEnumerable这个接口，所以也需要实现
35         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
36         {
37             return GetEnumerator();
38         }
39     }

  1     class Program
  2     {
  3         static void Main(string[] args)
  4         {
  5             BinaryTree<string> jfkFamilyTree = new BinaryTree<string>("root");//根节点
  6  
  7             jfkFamilyTree.Subitems = new Pair<BinaryTree<string>>(//左右树的根节点
  8                 new BinaryTree<string>("root-left"),
  9                 new BinaryTree<string>("root-right")
 10                 );
 11             jfkFamilyTree.Subitems.First.Subitems = new Pair<BinaryTree<string>>(//左子树的左右子树的根节点
 12                 new BinaryTree<string>("root-left-left"),
 13                 new BinaryTree<string>("root-left-right")
 14                 );
 15             jfkFamilyTree.Subitems.Second.Subitems = new Pair<BinaryTree<string>>(//右子树的左右子树的根节点
 16               new BinaryTree<string>("root-righ-left"),
 17               new BinaryTree<string>("root-righ-right")
 18              );
 19  
 20             //遍历二叉树
 21             foreach (string node in jfkFamilyTree)
 22             {
 23                 Console.WriteLine(node);
 24             }
 25  
 26  
 27  
 28             Console.ReadLine();
 29  
 30  
 31         }
 32  
 33  
 34     }
 35  
 36     //二叉树（根节点，左右子树)
 37     public class BinaryTree<T> : IEnumerable<T>
 38     {
 39  
 40         public BinaryTree(T value)
 41         {
 42             _value = value;
 43         }
 44  
 45         private T _value;//根节点
 46         public T Value
 47         {
 48             get { return _value; }
 49             set { _value = value; }
 50         }
 51         private Pair<BinaryTree<T>> _subitems;//子树,总共两个，左子树和右子数      
 52         public Pair<BinaryTree<T>> Subitems//子树元素，每一项都是一个树
 53         {
 54             get { return _subitems; }
 55             set
 56             {
 57                 IComparable first;
 58                 first = (IComparable)value.First.Value;
 59                 if (first.CompareTo(value.Second.Value) < 0)
 60                 {
 61                     //first is less than second.
 62                     //在这可以做处理，比如交换，或者报错提示
 63       //不过值类型赋值不会成功，需要使用其它方式，如换成类而不是struct
 64                 }
 65                 else
 66                 {
 67                     //first is not less than second.
 68                 }
 69                 _subitems = value;
 70             }
 71         }
 72         public IEnumerator<T> GetEnumerator()
 73         {
 74             yield return Value;//返回根节点
 75  
 76             foreach (BinaryTree<T> tree in Subitems)//遍历所有子树,从左向右遍历
 77             {
 78                 if (tree != null)
 79                 {
 80                     foreach (T item in tree)//遍历子树当中的所有节点,会引起BinaryTree<T>中的GetEnumerator()递归调用
 81                     {
 82                         yield return item;
 83                     }
 84  
 85                 }
 86             }
 87  
 88  
 89         }
 90         #region IEnumerable Members
 91         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
 92         {
 93             return GetEnumerator();
 94         }
 95         #endregion
 96  
 97  
 98     }
 99  
100     //子树类（左右子树)
101     public struct Pair<T> : IEnumerable<T>
102     {
103         private T _first;//左子树
104         private T _second;//右子树
105         public T First
106         {
107             get { return _first; }
108             set { _first = value; }
109         }
110         public T Second
111         {
112             get { return _second; }
113             set { _second = value; }
114         }
115  
116         public Pair(T first, T second)
117         {
118             _first = first;
119             _second = second;
120         }
121         #region IEnumerable<T>
122         public IEnumerator<T> GetEnumerator()
123         {
124             yield return First;
125             yield return Second;
126         }
127         #endregion
128  
129         #region IEnumerable Members
130         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
131         {
132             return GetEnumerator();
133         }
134         #endregion
135     }

 1             Pair<string> game = new Pair<string>("first","second");
 2  
 3            
 4             foreach (string name in game.GetReverseEnumerator())
 5             {
 6                 Console.WriteLine(name);
 7             }
 8  
 9     public struct Pair<T> : IEnumerable<T>
10     {
11  ...
12         public IEnumerable<T> GetReverseEnumerator()
13         {
14             yield return Second;
15             yield return First;
16         }
17     }