/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode() : val(0), next(nullptr) {} * ListNode(int x) : val(x), next(nullptr) {} * ListNode(int x, ListNode *next) : val(x), next(next) {} * }; */ class Solution { public: ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) { ListNode* L = new ListNode(0); ListNode* H = L; while(l1&&l2){ if(l1->val<=l2->val){ L->next = l1; l1 = l1->next; }else{ L->next = l2; l2 = l2->next; } L = L->next; } if(l1) L->next = l1; if(l2) L->next = l2; return H->next; } };