#leetcode#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.

按顺序合并两个链表

注意链表=初始化以及返回的问题

/** * 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) {        ListNode head(-1);        ListNode *tmp=&head;        while(l1&&l2)        {            if(l1->val<l2->val)            {                tmp->next=l1;                l1=l1->next;            }            else            {                tmp->next=l2;                l2=l2->next;            }            tmp=tmp->next;        }        if(l1)        {            tmp->next=l1;        }        if(l2)        {            tmp->next=l2;        }        return head.next;    }};