Invert Binary Tree

Invert a binary tree.

4
/ \
2 7
/ \ / \
1 3 6 9
to
4
/ \
7 2
/ \ / \
9 6 3 1
Trivia:
This problem was inspired by this original tweet by Max Howell:
Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.

//自己实现

/** * 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 {private:    void invert(TreeNode* root){        if(root==NULL)            return ;        invert(root->left);        invert(root->right);        TreeNode* temp = root ->right;        root ->right = root ->left;        root ->left = temp;    }public:    TreeNode* invertTree(TreeNode* root) {            invert(root);            return root;    }};

自己实现的过于繁琐，简易实现。

/** * 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:    TreeNode* invertTree(TreeNode* root) {            if(root){                invertTree(root->left);                invertTree(root->right);                swap(root->left,root->right);            }            return root;    }};