Symmetric Tree

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

    1
   / \
  2   2
 / \ / \
3  4 4  3

But the following is not:

    1
   / \
  2   2
   \   \
   3    3

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

struct TreeNode {
	int val;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

bool judgeSymmetric(TreeNode *L, TreeNode *R)
{
	if (!L&&!R)
		return true;
	else if (L&&R&&L->val == R->val)
		return judgeSymmetric(L->left, R->right) && judgeSymmetric(L->right, R->left);
	else
		return false;
}
bool isSymmetric(TreeNode *root) {
	if (root == NULL)
		return true;
	return judgeSymmetric(root->left, root->right);
}