21. Merge Two Sorted Lists
Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.
/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) { if(!l1)return l2; if(!l2)return l1; ListNode * p = l1; ListNode * q = l2; ListNode * res = new ListNode(-1); ListNode * tmp = res; while(p&&q){ if(p->val <= q->val){ tmp->next = p; tmp = p; p = p->next; }else if(p->val > q->val){ tmp->next = q; tmp = q; q = q->next; } } if(p) tmp->next = p; if(q) tmp->next = q; return res->next; } };