public void remove2(int num)
{
if (!Contains(num))
{
Console.WriteLine("value is not in the tree");
return;
}
BNode pointer = root;
BNode parent = root; // need a parent pointer so that root and pointer can be linked
while (pointer != null)
{
if (num < pointer.value)
{
parent = pointer;
pointer = pointer.left;
}
else if (num > pointer.value)
{
parent = pointer;
pointer = pointer.right;
}
else
{
break;
}
}
if (pointer.left == null && pointer.right == null)
{
// no children
if (pointer == root)
{
root = null;
}
else if (parent.left.value == pointer.value)
{
parent.left = null;
}
else if (parent.right.value == pointer.value)
{
parent.right = null;
}
pointer = null;
}
else if (pointer.left != null && pointer.right == null)
{
// one child left
if (pointer == root)
{
root = pointer.left;
}
else if (parent.left.value == pointer.value)
{
parent.left = pointer.left;
}
else if (parent.right.value == pointer.value)
{
parent.right = pointer.left;
}
pointer = null;
}
else if (pointer.left == null && pointer.right != null)
{
// one child right
if (pointer == root)
{
root = pointer.right;
}
else if (parent.left.value == pointer.value)
{
parent.left = pointer.right;
}
else if (parent.right.value == pointer.value)
{
parent.right = pointer.right;
}
pointer = null;
}
else
{
// two children
// swap value with rightmost node of left subtree
BNode RightMostOfLeft = iop(pointer.left);
if (pointer == root)
{
root.value = RightMostOfLeft.value;
}
else if (parent.left.value == pointer.value)
{
parent.left.value = RightMostOfLeft.value;
}
else if (parent.right.value == pointer.value)
{
parent.right.value = RightMostOfLeft.value;
}
// traverse to the parent node of the rightmost node
parent = pointer;
pointer = pointer.left;
while (pointer.right != null && pointer.right.right != null)
{
pointer = pointer.right;
}
// remove rightmost node
if (pointer.right != null)
{
pointer.right = pointer.right.left;
}
else
{
parent.left = pointer.left;
}
}
}
public BNode(int v)
{
value = v;
left = null;
right = null;
}
public BST()
{
root = null;
}