void postOrder(Node *root) { if (root == NULL) { return; // Base case: if node is null, just return } postOrder(root->left); // Traverse left subtree postOrder(root->right); // Traverse right subtree cout << root->data << " "; // Visit the root node (print data) }

My Java solution with o(n) time complexity and o(h) space complexity:

public static void postOrder(Node root) {
        if(root == null) return;
        
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.data + " ");
    }

Python

def postOrder(root):
    #Write your code here
    if root is None:
        return
    
    postOrder(root.left)
    
    postOrder(root.right)
    
    print(root.info,end=" ")

Very Simple Recursive JavaScript Solution:

const resp = []

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

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

It is asking how to use process.stdout.write to print your answer on JS, not testing the Tree concept.