/// <summary>
/// Add a member to a binary serach tree
/// </summary>
/// <param name="aMember"> member to add </param>
/// <param name="ptr"> a binary serach tree node </param>
private void add(Member aMember, BTreeNode ptr)
{
if (aMember.CompareTo(ptr.Member) < 0)
{
if (ptr.LChild == null)
{
ptr.LChild = new BTreeNode(aMember);
}
else
{
add(aMember, ptr.LChild);
}
}
else
{
if (ptr.RChild == null)
{
ptr.RChild = new BTreeNode(aMember);
}
else
{
add(aMember, ptr.RChild);
}
}
}
// pre: ptr != null
// post: item is inserted to the binary search tree rooted at ptr
private void Insert(Member item, BTreeNode ptr)
{
if (item.CompareTo(ptr.Item) < 0)
{
if (ptr.LChild == null)
{
ptr.LChild = new BTreeNode(item);
}
else
{
Insert(item, ptr.LChild);
}
}
else
{
if (ptr.RChild == null)
{
ptr.RChild = new BTreeNode(item);
}
else
{
Insert(item, ptr.RChild);
}
}
}
private bool Search(Member item, BTreeNode r)
{
if (r != null)
{
if (item.CompareTo(r.Member) == 0)
{
return(true);
}
else
if (item.CompareTo(r.Member) < 0)
{
return(Search(item, r.LChild));
}
else
{
return(Search(item, r.RChild));
}
}
else
{
return(false);
}
}
/// <summary>
/// Delete a member from the mamber collection
/// </summary>
/// <param name="aMember"> member to delete </param>
public void delete(Member aMember)
{
// search for item and its parent
BTreeNode ptr = root; // search reference
BTreeNode parent = null; // parent of ptr
while ((ptr != null) && (aMember.CompareTo(ptr.Member) != 0))
{
parent = ptr;
if (aMember.CompareTo(ptr.Member) < 0) // move to the left child of ptr
{
ptr = ptr.LChild;
}
else
{
ptr = ptr.RChild;
}
}
if (ptr != null) // if the search was successful
{
number--;
// case 3: item has two children
if ((ptr.LChild != null) && (ptr.RChild != null))
{
// find the right-most node in left subtree of ptr
if (ptr.LChild.RChild == null) // a special case: the right subtree of ptr.LChild is empty
{
ptr.Member = ptr.LChild.Member;
ptr.LChild = ptr.LChild.LChild;
}
else
{
BTreeNode p = ptr.LChild;
BTreeNode pp = ptr; // parent of p
while (p.RChild != null)
{
pp = p;
p = p.RChild;
}
// copy the item at p to ptr
ptr.Member = p.Member;
pp.RChild = p.LChild;
}
}
else // cases 1 & 2: item has no or only one child
{
BTreeNode c;
if (ptr.LChild != null)
{
c = ptr.LChild;
}
else
{
c = ptr.RChild;
}
// remove node ptr
if (ptr == root) //need to change root
{
root = c;
}
else
{
if (ptr == parent.LChild)
{
parent.LChild = c;
}
else
{
parent.RChild = c;
}
}
}
}
}
