static void Main(string[] args)
{
Node root = new Node(10);
root.left = new Node(8);
root.left.left = new Node(7);
root.left.right = new Node(9);
root.right = new Node(12);
root.right.left = new Node(11);
root.right.right = new Node(13);
Node header = null;
convertBSTToDLL(root, ref header);
}
public static void convertBSTToDLLCore(Node root, ref Node lastNodeInDLList)
{
if (root == null)
return;
Node currentNode = root;
convertBSTToDLLCore(root.left, ref lastNodeInDLList);
currentNode.left = lastNodeInDLList;
if (lastNodeInDLList != null) // avoid crash
lastNodeInDLList.right = currentNode;
lastNodeInDLList = currentNode;
convertBSTToDLLCore(root.right, ref lastNodeInDLList);
return;
}
// using divide and conquer techniques; another solution is to use node rotation
public static void convertBSTToDLL(Node root, ref Node header)
{
if (root == null)
{
header = null;
return;
}
Node lastNode = null;
convertBSTToDLLCore(root, ref lastNode);
// we need to get the header node; go upper to the last node and find the header
header = lastNode; // test cases: null, one node, more than one, ...
while (lastNode != null && lastNode.left !=null)
{
header = lastNode.left;
lastNode = lastNode.left;
}
}