LeetCode101题：判断一棵二叉树是否为对称二叉树

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */

bool help(struct TreeNode* root1,struct TreeNode* root2)
{
    if(root1==NULL&&root2==NULL)
    return true;
    if(root1==NULL||root2==NULL)
    return false;
    return (root1->val==root2->val)&&help(root1->left,root2->right)&&help(root1->right,root2->left);
}
bool isSymmetric(struct TreeNode* root){
   return help(root,root);

}