剑指offer刷题（二十）

二叉树的镜像

请完成一个函数，输入一个二叉树，该函数输出它的镜像。

例如输入：

示例 1：

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

限制：

0 <= 节点个数 <= 1000

解题思路：

java

/**
 * 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 root;
        TreeNode tmp = root.right;
        root.right = mirrorTree(root.left);
        root.left = mirrorTree(tmp);
    
        return root;
    }
}

python

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def mirrorTree(self, root):
        """
        :type root: TreeNode
        :rtype: TreeNode
        """
        if not root:
            return root
        tmp = root.right
        root.right =self.mirrorTree(root.left)
        root.left = self.mirrorTree(tmp)
        return root