第十七题（二叉树的镜像）：操作给定的二叉树，将其变换为源二叉树的镜像。

二叉树的镜像定义：源二叉树 
           8
          /  \
         6   10
        / \  / \
       5  7 9 11
       镜像二叉树
           8
          /  \
         10   6
        / \  / \
       11 9 7  5

Python:

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    # 返回镜像树的根节点
    def Mirror(self, root):
        # write code here
        if not root:
            return root
        root.left, root.right = root.right, root.left
        self.Mirror(root.left)
        self.Mirror(root.right)
        return root

Java:

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    public void Mirror(TreeNode root) {
        if(root == null)
            return ;
        TreeNode tmp = root.left;
        root.left = root.right;
        root.right = tmp;
        Mirror(root.left);
        Mirror(root.right);
    }
}