package nowcoder; public class Mirror { class TreeNode{ int val=0; TreeNode left=null; TreeNode right=null; public TreeNode(int val){ this.val=val; } } public void Mirror(TreeNode root){ if(root==null) return; if(root.left==null && root.right==null) return; TreeNode node=root.left; root.left=root.right; root.right=node; if(root.left!=null){ Mirror(root.left); } if(root.right!=null){ Mirror(root.right); } } }