public class BinaryTree:NaryTree

     {

         //构造二叉空树

         public BinaryTree():base(2)

         {

              //

              // TODO: 在此处添加构造函数逻辑

              //

         }

         public BinaryTree(object _obj):base(2,_obj)

         {}

//------------------------------------------------------------------

         protected override object GetEmptyInstance(uint _degree)

         {    return new BinaryTree(_degree); }

//------------------------------------------------------------------

         //重写深度遍历

         public override void DepthFirstTraversal(IPrePostVisitor _vis)

         {

              if ( !IsEmpty() )

              {

                   _vis.PreVisit(this.Key);

                   this[0].DepthFirstTraversal(_vis);

                   _vis.Visit(this.Key);

                   this[1].DepthFirstTraversal(_vis);

                   _vis.PostVisit(this.Key);

              }

         }

         //二叉树大小的比较

         //先比较关键字，如果相等，再比较左子树，如果再相等，则比较右子树----如此递归

         #region IComparable 成员

         public override int CompareTo(object obj)

         {

              // TODO:  添加 BinaryTree.CompareTo 实现

              //因为Comare()中已经进行了类型断定，故不会出现转型错误

              BinaryTree tmpTree=(BinaryTree)obj;

              if( this.IsEmpty() )

                   return tmpTree.IsEmpty()?0:-1;

              if( tmpTree.IsEmpty() )

                   return 1;

              int result=Comparer.Default.Compare(this,tmpTree);

              if(result==0)

                   result=this[0].CompareTo(tmpTree[0]);

              if(result==0)

                   result=this[1].CompareTo(tmpTree[1]);

              return result;

         }

         #endregion

     }

}