package Tree; //ÏÈÐò±éÀú public class Recursion { public static void scanNodes(TreeNode root){ if(root!=null){ System.out.println("this is node: "+root.val); scanNodes(root.left); System.out.println("node"+root.val+" finish scanning left"); scanNodes(root.right); System.out.println("node"+root.val+" finish scanning right"); } } public static void main(String[] args) { TreeNode root = new TreeNode(1); TreeNode left1 = new TreeNode(2); TreeNode right1 = new TreeNode(3); TreeNode left2 = new TreeNode(4); TreeNode right2 = new TreeNode(5); TreeNode right3 = new TreeNode(6); //create one tree root.left = left1; root.right = right1; left1.left = left2; left1.right = right2; right1.right = right3; scanNodes(root); } }