Invert a Binary Tree

/*
	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)
			return NULL;
		TreeNode* tempNode = root->left;
		root->left = invertTree(root->right);
		root->right = invertTree(tempNode);
		return root;
	}
};