Inorder Traversal without Recursion

InorderIterative.java

public ArrayList<Integer> inorderTraversal(TreeNode A) {
        
        Stack<TreeNode> stack = new Stack();
        TreeNode current = A;
        ArrayList<Integer> result = new ArrayList<Integer>();
         while(current != null || !stack.isEmpty()){
             while(current != null){
                 stack.push(current);
                 current = current.left;
             }
             
             current = stack.pop();
             result.add(current.val);
             current = current.right;
         }
        return result;
    }