这么简单的二叉树算法都不会？

bool isSame(TreeNode* a, TreeNode* b) {    if (a == nullptr && b == nullptr) return true;    else if (a == nullptr || b == nullptr) return false;    else return a->val == b->val && isSame(a->left, b->left) && isSame(a->right, b->right);}

bool isSubtree(TreeNode* root, TreeNode* subRoot) {    if (root == nullptr && subRoot == nullptr) return true;    else if (root == nullptr || subRoot == nullptr) return false;    else return isSame(root, subRoot) || isSubtree(root->left, subRoot) || isSubtree(root->right, subRoot);}

$ md5sum a.c6004b6a21b274b405a2bd1f1c75a93c7  a.c

void serialize(TreeNode* root, string& str) {    if (root == nullptr) {        str = str + "#";    } else {        str = str  + "," + to_string(root->val);
        serialize(root->left, str);        serialize(root->right, str);    }}

bool isSubtree(TreeNode* root, TreeNode* subRoot) {    string a, b;    serialize(root, a);    serialize(subRoot, b);    return a.find(b)!=string::npos;}