java-15.输入一颗二元查找树，将该树转换为它的镜像， 即在转换后的二元查找树中，左子树的结点都大于右子树的结点。 用递归和循环

//use recursion
	public static void mirrorHelp1(Node node){
		if(node==null)return;
		swapChild(node);
		mirrorHelp1(node.getLeft());
		mirrorHelp1(node.getRight());
	}
	//use no recursion but stack
	public static void mirrorHelp2(Node node){
		if(node==null)return;
		Stack<Node> stack=new Stack<Node>();
		stack.add(node);
		while(!stack.isEmpty()){
			node=stack.pop();
			swapChild(node);
			if(node.getLeft()!=null){
				stack.push(node.getLeft());
			}
			if(node.getRight()!=null){
				stack.push(node.getRight());
			}
				
		}
	}

	public static void swapChild(Node node){
		/*not like c/c++,you cannot do this:
		Node temp=left;
		left=right;
		right=temp;
		*/
		Node left=node.getLeft();
		node.setLeft(node.getRight());
		node.setRight(left);
	}