226. Invert Binary Tree

原文题目：

https://leetcode.com/problems/invert-binary-tree/description/

AC代码：

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 (NULL == root)
		{
			return NULL;
		}
		/*交换左右子树*/
		TreeNode* temp = root->left;
		root->left = root->right;
		root->right = temp;

		/*递归左右子树*/
		invertTree(root->left);
		invertTree(root->right);

		return root;

	}
};