leetcode Symmetric Tree

可以利用与same tree类似的方法

class Solution {public:    bool isSymmetric(TreeNode *root) {        if(root==NULL)            return true;        return isSymmetricHelper(root->left, root->right);            }        bool isSymmetricHelper(TreeNode *p, TreeNode *q)    {                  if(p==q&&p==NULL)            return true;                    if((!p&&q)||(p&&!q)||p->val!=q->val)            return false;         return isSymmetricHelper(p->left, q->right)&&isSymmetricHelper(p->right, q->left);                    }};