Algorithm for Preorder Tree Traversals : Recursive Way

//Preorder Tree Traversals : Recursive class BinaryTreePreOrderTraversalR {       class TreeNode {              TreeNode left, right;              int data; // considering integer data.                     public TreeNode(int dataItem) {                   this.data = dataItem;                   left = null;                   right = null;              }       }               TreeNode root;        BinaryTreePreOrderTraversalR() {              root = null;        }               void printPerOrderTraversal(TreeNode treeNode) {              if(treeNode == null)                     return;                           //Data, Left, Right              System.out.println(treeNode.data);              printPerOrderTraversal(treeNode.left);              printPerOrderTraversal(treeNode.right);        }               void printPerOrder() {              printPerOrderTraversal(root);        }        public static void main(String[] args) {              BinaryTreePreOrderTraversalR tree = new BinaryTreePreOrderTraversalR();              tree.root = new TreeNode(1);                      tree.root.left = new TreeNode(2);              tree.root.right = new TreeNode(3);                      tree.root.left.left = new TreeNode(4);              tree.root.left.right = new TreeNode(5);                      tree.root.right.left = new TreeNode(6);              tree.root.right.right = new TreeNode(7);                      tree.printPerOrder();        } } //Time Complexity: O(n). Space Complexity: O(n).

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