public List preorderTraversal(TreeNode root) { List list = new LinkedList(); Stack<div>stack = new Stack<div>(); stack.push(root); while(stack.empty()==false) { TreeNode n=stack.pop(); if(n!=null) { list.add(n.val); stack.push(n.right); stack.push(n.left); } } return list; } Void postorder(Node root) { List list = new LinkedList(); Stack<div>stack1 = new Stack<div>(); Stack stack2= new Stack(); If(root!=null)Stack1.push(root); while(stack1.empty()==false) { TreeNode n=stack1.pop(); Stack2.push(n.val); if(n!=null) { Stack1.push(n.left); Stack1.push(n.right); } } While(stack2.empty()==false) { List.add(stack2.pop()); } return list; } List inorder(Node root) { List list = new LinkedList(); Stack<div>stack = new Stack<div>(); TreeNode n=root; While(n!=null) { stack.push(n); n=n.left; } while(stack.empty()==false) { n=stack.pop(); list.add(n.val); n=n.right; While(n!=null) { stack.push(n); n=n.left; } } return list; }</div></div></div></div></div></div>