Solution 15: 树的镜像

问题描述

输入一颗BST，将该树转换为它的镜像。

要求使用递归和非递归两种思路解决。

 

解决思路

非递归基于BST。

 

程序

public class MirrorOfBST {
public void toMirrorRec(TreeNode root) {
	if (root == null) {
		return ;
	}
	
	TreeNode left = root.left;
	TreeNode right = root.right;
	
	root.left = right;
	root.right = left;
	
	toMirrorRec(left);
	toMirrorRec(right);
}

public void toMirrorNoRec(TreeNode root) {
	if (root == null) {
		return ;
	}
	
	Queue<TreeNode> queue = new LinkedList<TreeNode>();
	queue.offer(root);
	
	while (!queue.isEmpty()) {
		TreeNode node = queue.poll();
		if (node != null) {
			TreeNode left = node.left;
			TreeNode right = node.right;
			
			node.left = right;
			node.right = left;
			
			queue.offer(right);
			queue.offer(left);
		}
	}
}
}