二叉树的镜像

    import java.util.LinkedList;  
      
    public class MirrorTest  
    {  
        //递归  
       public void Mirror(TreeNode root)  
       {  
           if(root == null)  
            return;  
           else  
            {  
                
               TreeNode temp = root.left;//交换根节点的左右孩子  
               root.left = root.right;  
               root.right = temp;  
               Mirror(root.left);//镜像根节点的左孩子的左右子树  
               Mirror(root.right);//镜像根节点的右孩子的左右子树  
            }  
       }  
         
       //非递归实现  
       public void Mirror1(TreeNode root)  
       {  
           if(root == null)  
           {  
               return;  
           }  
         LinkedList<TreeNode> stack = new LinkedList<TreeNode>();//借助于辅助栈  
         TreeNode current = null;//存放出栈的栈顶元素  
         TreeNode temp = null;  
         stack.push(root);//将根元素入栈  
         while(!stack.isEmpty())  
         {  
            current = stack.pop();//将根元素出栈 交换根元素的左右子树  
            if(current.left != null || current.right != null)//若左右孩子不为空则交换左右孩子  
            {  
                temp = current.left;  
                current.left = current.right;  
                current.right = temp;  
            }  
            //将根元素的左右孩子压入栈中    
            if(current.left != null)  
                stack.push(current.left);  
            if(current.right != null)  
                stack.push(current.right);  
         }  
         
       }  
    }