class Solution {
    public void mirror(TreeNode root) {
         if(root==null) return ;
         Queue<TreeNode> queue=new LinkedList<>();
          queue.add(root);
          while(!queue.isEmpty()){
              int n=queue.size();
              for(int i=0;i<n;i++){
                  TreeNode cur=queue.poll();
                   TreeNode temp=cur.left;
                   cur.left=cur.right;
                   cur.right=temp;
                   if(cur.left!=null) queue.add(cur.left);
                   if(cur.right!=null) queue.add(cur.right);
              } 
          }

    }
}