My Java solution with linear time complexity and constant space complexity:

public static void preOrder(Node root) {
        if(root == null) return; //no val to be printed
        
        //print val
        System.out.print(root.data + " ");
        
        //recursively traverse thru left nodes first, the through right nodes
        preOrder(root.left);
        preOrder(root.right);
    }

Very Simple Javascript Recursive Solution

const resp = []

function helperFunc(root) { if(!root) return; resp.push(root.data) helperFunc(root.left); helperFunc(root.right); }

function preOrder(root) { helperFunc(root); console.log(resp.join(' ')); }

Very Simple Javascript Recursive Solution

const resp = []

function helperFunc(root) { if(!root) return; resp.push(root.data) helperFunc(root.left); helperFunc(root.right); }

function preOrder(root) { helperFunc(root); console.log(resp.join(' ')); }

class Node: def init(self, info): self.info = info
self.left = None
self.right = None self.level = None

def __str__(self):
    return str(self.info) 

class BinarySearchTree: def init(self): self.root = None

def create(self, val):  
    if self.root == None:
        self.root = Node(val)
    else:
        current = self.root

        while True:
            if val < current.info:
                if current.left:
                    current = current.left
                else:
                    current.left = Node(val)
                    break
            elif val > current.info:
                if current.right:
                    current = current.right
                else:
                    current.right = Node(val)
                    break
            else:
                break

""" Node is defined as self.left (the left child of the node) self.right (the right child of the node) self.info (the value of the node) """ def preOrder(root): if(root==None): return 0 print(root.info, end=" ") preOrder(root.left) preOrder(root.right)

tree = BinarySearchTree() t = int(input())

arr = list(map(int, input().split()))

for i in range(t): tree.create(arr[i])

preOrder(tree.root)

JavaScript solution using recursion

function preOrder(root) {
    let res = '';
    function abc(root){
      if(root){
        res = res + root.data + '  ';
        abc(root.left);
        abc(root.right)  
       }
    }
    abc(root);
    console.log(res)
}