면접 문제두 갈래 나무의 거울

제목

     4
   /   \
  2     7
 / \   / \
1   3 6   9

     4
   /   \
  7     2
 / \   / \
9   6 3   1

예제

 ：root = [4,2,7,1,3,6,9]
 ：[4,7,2,9,6,3,1]

코드

     4              4              4
   /   \          /   \          /   \
  2     7   ==>  7     2   ==>  7     2
 / \   / \      / \   / \      / \   / \
1   3 6   9    6   9 1   3    9   6 3   1

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode mirrorTree(TreeNode root) {
        if (root == null) {
            return null;
        }
        // 
        TreeNode temp = root.left;
        root.left = mirrorTree(root.right);
        root.right = mirrorTree(temp);
        return root;
    }
}

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode mirrorTree(TreeNode root) {
        if (root == null) {
            return null;
        }
        Deque<TreeNode> queue = new ArrayDeque<>();
        queue.addLast(root);
        while (queue.size() != 0) {
            TreeNode node = queue.removeLast();
            if (node.left != null) {
                queue.addLast(node.left);
            }
            if (node.right != null) {
                queue.addLast(node.right);
            }
            TreeNode temp = node.left;
            node.left = node.right;
            node.right = temp;
        }
        return root;
        
    }
}