源代码namespace BST
{
public class Node
{
public int Value;
public Node Left;
public Node Right;
}
public class BSTree
{
private Node root;
public void Insert(int x)
{
Node v = new Node() { Value = x };
if (root == null)
{
root = v;
return;
}
Node preNode = PosToInsert(x);
if (preNode.Value > x)
{
preNode.Left = v;
}
else
{
preNode.Right = v;
}
}
//return decessor node, the biggest node in left subtree of x
private Node Predecessor(Node x)
{
if (x == null || x.Left == null)
{
return null;
}
Node node = x.Left;
while (node.Right != null)
{
node = node.Right;
}
return node;
}
private Node ParentNode(Node node)
{
return ParentNode(node.Value);
}
private Node ParentNode(int x)
{
Node node = root;
Node parent = node;
while (node != null)
{
if (node.Value == x)
{
return parent;
}
parent = node;
if (node.Value > x)
{
node = node.Left;
}
else
{
node = node.Right;
}
}
throw new Exception(string.Format("{0} has no parent",x));
}
//return a node ,should insert x as a child to it
private Node PosToInsert(int x)
{
Node node = root;
Node posToInsert = null;
while (node != null)
{
posToInsert = node;
if (node.Value == x)
{
throw new Exception(string.Format("{0} already exist in tree", x));
}
else if (node.Value > x)
{
node = node.Left;
}
else
{
node = node.Right;
}
}
return posToInsert;
}
public Node Search(int x)
{
return Search(root, x);
}
public Node Search(Node node, int x)
{
if (node == null)
{
return null;
}
if (node.Value == x)
{
return node;
}
else if (node.Value > x)
{
return Search(node.Left, x);
}
else
{
return Search(node.Right, x);
}
}
public void Remove(int x)
{
Node node=Search(x);
if (node == null)
{
throw new Exception(string.Format("{0} not exist in tree",x));
}
if (node.Left == null && node.Right == null)
{
node = null;
}
else if (node.Left != null && node.Right != null)
{
Node preNode = Predecessor(node);
Node parentNode = ParentNode(preNode);
Swap(ref preNode.Value,ref node.Value);
if (Object.ReferenceEquals(preNode, parentNode.Left))
{
parentNode.Left = null;
}
else
{
parentNode.Right = null;
}
}
else if (node.Left != null)
{
Node parentNode = ParentNode(node);
if (Object.ReferenceEquals(node, parentNode.Left))
{
parentNode.Left = node.Left;
}
else
{
parentNode.Right = node.Left;
}
}
else if (node.Right != null)
{
Node parentNode = ParentNode(node);
if (Object.ReferenceEquals(node, parentNode.Left))
{
parentNode.Left = node.Right;
}
else
{
parentNode.Right = node.Right;
}
}
}
public override string ToString()
{
return Tree(root);
}
private string Tree(Node node)
{
if (node == null)
{
return string.Empty;
}
string left = Tree(node.Left);
string right = Tree(node.Right);
if (!string.IsNullOrEmpty(left) || !string.IsNullOrEmpty(right))
{
return string.Format("{0}({1},{2})", node.Value, Tree(node.Left), Tree(node.Right));
}
else
{
return node.Value.ToString();
}
}
public static void Swap(ref int x, ref int y)
{
int temp = x;
x = y;
y = temp;
}
}
}
