ListNode* insert(vector<int>& A, int val) { // write code here if(A.empty()) return nullptr; ListNode *pre = new ListNode(0); ListNode *cur = pre; int c = 1; for(int i : A) { if(val < i && c > 0) { cur->next = new ListNode(val); cur = cur->next; c--; } cur->next = new ListNode(i); cur = cur->next; } if(c>0) { cur->next = new ListNode(val); cur = cur->next; } return pre->next;