Algoritm for Postorder Tree Traversals : Recursive Way

//Postorder Tree Traversals : Recursive class BinaryTreePostOrderTraversalR {      class TreeNode {             TreeNode left, right;             int data; // considering integer data.                   public TreeNode(int dataItem) {                   this.data = dataItem;                   left = null;                   right = null;             }      }             TreeNode root;        BinaryTreePostOrderTraversalR() {              root = null;        }               void printPostOrderTraversal(TreeNode treeNode) {              if(treeNode == null)                     return;                           //Right, Left, Data              printPostOrderTraversal(treeNode.right);              printPostOrderTraversal(treeNode.left);              System.out.println(treeNode.data);        }               void printPostOrder() {              printPostOrderTraversal(root);        }        public static void main(String[] args) {              BinaryTreePostOrderTraversalR tree = new BinaryTreePostOrderTraversalR();              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.printPostOrder();        } } //Time Complexity: O(n). Space Complexity: O(n).

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