LeetCode: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.
这道题有一个梗,homebrew的作者去Google面试就被问了这道题，结果他想了半天 没 想 出 来！哈哈哈class Solution {
public:
TreeNode* invertTree(TreeNode* root) {
if(root==NULL||root->left==NULL&&root->right==NULL){
return root;
}
TreeNode* temp=root->left;
root->left=root->right;
root->right=temp;
if(root->left){
invertTree(root->left);
}
if(root->right){
invertTree(root->right);
}
return root;
}
};