判斷兩樹是否相同
bool isSameTree(struct TreeNode* p, struct TreeNode* q) {
if (p == NULL && q == NULL) {
return true;
}
if (p == NULL || q == NULL) {
return false;
}
return p->val == q->val
&& isSameTree(p->left, q->left)
&& isSameTree(p->right, q->right);
}