# Find kth smallest element in BST kotlin

Kotlin program for Find kth smallest element in BST. Here more solutions.

``````// Kotlin program for
// K’th smallest element in Binary Search Tree
class TreeNode
{
var data: Int;
var left: TreeNode ? ;
var right: TreeNode ? ;
constructor(data: Int)
{
this.data = data;
this.left = null;
this.right = null;
}
}
class BinarySearchTree
{
var root: TreeNode ? ;
var counter: Int;
var element: TreeNode ? ;
constructor()
{
this.root = null;
this.counter = 0;
this.element = null;
}
// Insert a node element
fun insert(node: TreeNode ? , data : Int): TreeNode ?
{
if (node != null)
{
if (node.data >= data)
{
// When new element is smaller or equal to current node
node.left = this.insert(node.left, data);
}
else
{
// When new element is higher to current node
node.right = this.insert(node.right, data);
}
// Important to manage new node
return node;
}
else
{
return TreeNode(data);
}
}
// Find the kth smallest node in BST
fun findKthSmallest(node: TreeNode ? , k : Int): Unit
{
if (node != null)
{
// Visit left subtree
this.findKthSmallest(node.left, k);
if (this.counter == k)
{
// Stop recursion
return;
}
if (this.element == null ||
this.element!!.data < node.data)
{
// Modified counter variable by one
this.counter += 1;
// Collect possible result
this.element = node;
}
// Visit right subtree
this.findKthSmallest(node.right, k);
}
}
fun printKthSsmallest(k: Int): Unit
{
if (k <= 0)
{
// When given k is not valid positive values
println("Invalid node position " + k);
}
else if (this.root == null)
{
// When BST are no have elements
println("Empty Binary Search Tree");
}
else
{
// Reset values
this.counter = 0;
this.element = null;
// Find result
this.findKthSmallest(this.root, k);
if (this.counter < k)
{
// If In case given kth smallest node are
// Not exist in binary search tree, then
println("Given " + k +
" smallest node are not exist " + this.counter);
}
else
{
println("[" + k +
"] smallest node : " + this.element!!.data);
}
}
}
// Handle request to add new node
{
this.root = this.insert(this.root, key);
}
}
fun main(args: Array < String > ): Unit
{
val tree: BinarySearchTree = BinarySearchTree();
/*
Make Tree
----------
7
/ \
/   \
4     9
/ \   / \
3   5 8   10
/
4
*/
// Testing
tree.printKthSsmallest(6);
tree.printKthSsmallest(4);
tree.printKthSsmallest(3);
}``````

Output

``````[6] smallest node : 9
[4] smallest node : 7
[3] smallest node : 5``````

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