10. Insert a given node in BST Medium
11. Delete a node in BST Medium
12. Check if a tree is a BST or not Medium
13. LCA in BST Medium
14. Construct a BST from a preorder traversal Medium
15. Inorder Successor/Predecessor in BST Medium
16. Merge 2 BST's Hard
17. Two Sum In BST | Check if there exists a pair with Sum K Hard
18. Correct BST with two nodes swapped Hard
19. Largest BST in Binary Tree Hard
20. Kth Smallest and Largest element in BST Medium