//Logic: we can find the kth smallest by many ways
//1) we can build sorted array from preorder traversal and find the kth smalles on the sorted array
//2) we can put items on stack and when stack count reaches k return the element
//3) use static count inside the method and when k reaches counter return the element
//public KarthicBTNode<int> FindkthsmallestnodebyInordertraversal(KarthicBTNode<int> root, int k, Stack<KarthicBTNode<int>> mystack)
//{
// //base case
// if (root != null)
// {
// //left
// FindkthsmallestnodebyInordertraversal(root.Left, k, mystack);
// //current
// mystack.Push(root);
// if (k == mystack.Count)
// {
// return root;
// }
// //right
// FindkthsmallestnodebyInordertraversal(root.Right, k, mystack);
// }
//}
public BTCustomNode <int> FindkthsmallestnodebyInordertraversal(KarthicBTNode <int> root, int k, Stack <KarthicBTNode <int> > mystack)
{
//base case
if (root == null)
{
return(null);
}
//left
BTCustomNode <int> ltree = FindkthsmallestnodebyInordertraversal(root.Left, k, mystack);
if (ltree != null && ltree.IsSmallest)
{
return(ltree);
}
//current
BTCustomNode <int> current = new BTCustomNode <int>();
current.node = root;
mystack.Push(root);
if (k == mystack.Count)
{
current.IsSmallest = true;
return(current);
}
else
{
current.IsSmallest = false;
}
//right
BTCustomNode <int> rtree = FindkthsmallestnodebyInordertraversal(root.Right, k, mystack);
if (rtree != null && rtree.IsSmallest)
{
return(rtree);
}
return(current);
}
private BTCustomNode <int> FindKthLargestByTraversal(KarthicBTNode <int> node, int k, Stack <KarthicBTNode <int> > mystack)
{
if (node == null)
{
BTCustomNode <int> basetree = new BTCustomNode <int>();
basetree.node = null;
return(basetree);
}
//traverse right child
BTCustomNode <int> righttree = new BTCustomNode <int>();
righttree = FindKthLargestByTraversal(node.Right, k, mystack);
if (righttree.node != null && righttree.IsLargest)
{
return(righttree);
}
//visit current
BTCustomNode <int> current = new BTCustomNode <int>();
mystack.Push(node);
current.node = node;
if (mystack.Count == k)
{
current.IsLargest = true;
return(current);
}
else
{
current.IsLargest = false;
}
BTCustomNode <int> lefttree = new BTCustomNode <int>();
lefttree = FindKthLargestByTraversal(node.Left, k, mystack);
if (lefttree.node != null && lefttree.IsLargest)
{
return(lefttree);
}
return(current);
}