Leetcode notes: Invert Binary Tree

I. Title Description

Invert a binary tree.

     4   /     2     \   1   3 6   9

To

     4   /     7     \   9   6 3   1

Trivia:

This problem is inspired by this original tweets by Max Howell:

google:90% of our engineers with the software you wrote (Homebrew), but can ' t invert a binary tree on a whiteboard so Fuck off.

Two. Topic analysis

The subject intention is obvious, namely flipping a binary tree. The following is a few words, the approximate meaning is:

Google: We have 90% of our engineers using the software you wrote (Homebrew? , but you're not going to flip a binary tree on the whiteboard, it's fucked.

This is a problem that any programmer should have, recursive or queue iterative solution can be achieved, do not add more than repeat.

Three. Sample code

// C++，递归/** * 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:    invertTree(TreeNode* root) {        ifreturn root;        TreeNode* temp = root->left;        root->left = root->right;        root->right = temp;        invertTree(root->left);        invertTree(root->right);        return root;    }};

# Python, recursive# Definition for a binary tree node.# class TreeNode:# def __init__ (self, x):# self.val = x# self.left = None# self.right = None class solution(object):     def inverttree(self, root):        "" : Type Root:TreeNode:rtype:TreeNode "" "        ifRoot is None:return NoneRoot.left, root.right = Root.right, Root.left self.inverttree (root.left) self.inverttree (root.right)returnRoot

Four. Summary

The test instructions helps us to review the basis of the data structure.

Leetcode notes: Invert Binary Tree