SearchInABinarySearchTree.java

/* You are given the root of a binary search tree (BST) and an integer val.
 * Find the node in the BST that the node's value equals val and return the subtree rooted with that node.
 * If such a node does not exist, return null.
 *
 * Example 1 : Input : root = [4,2,7,1,3], val = 2
 * Output : [2,1,3]
 * 
 * Example 2 : Input : root = [4,2,7,1,3], val = 5
 * Output : []
 */
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */

class SearchInABinarySearchTree {
    public TreeNode searchBST(TreeNode root, int val) {
        if(root == null) return null;
        if(root.val == val) return root;

        if (val < root.val) return searchBST(root.left, val);
        if (val > root.val) return searchBST(root.right, val);
        
        return null;
    }
}