剑指offer27 二叉树的镜像

剑指offer27 二叉树的镜像

    输入一个二叉树，将它变换为它的镜像。

样例

输入树：

          8
         / \
        6  10
       / \ / \
      5  7 9 11

 [8,6,10,5,7,9,11,null,null,null,null,null,null,null,null] 
 
输出树：

          8
         / \
        10  6
       / \ / \
      11 9 7  5

 [8,10,6,11,9,7,5,null,null,null,null,null,null,null,null]

思路：

    依次递归交换左右子树，直到为空。

AcWing-38 C++代码：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void mirror(TreeNode* root) {
        if(root == NULL){
            return;
        }

        TreeNode* temp = root->left;
        root->left = root->right;
        root->right = temp;
        
        mirror(root->left);
        mirror(root->right);
    }
};

AcWing-38 python代码：

# 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 mirror(self, root):
        """
        :type root: TreeNode
        :rtype: void
        """
        if root == None:
            return
        
        root.left, root.right = root.right, root.left
        
        self.mirror(root.left)
        self.mirror(root.right)