LeetCode 刷题： 左右反转一个二叉树

/**
* 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 != NULL)
{
TreeNode *temp = root->left;
root->left = root->right;
root->right = temp;

invertTree(root->left);
invertTree(root->right);
}
return root;
}
};

Invert a binary tree.

4
/   \
2     7
/ \   / \
1   3 6   9

to

4
/   \
7     2
/ \   / \
9   6 3   1

解法：

递归法：