Merge Two Sorted Lists

题目描述：

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.

链表的归并排序，AC代码如下：

class Solution {public:ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {ListNode* dumpHead = new ListNode(-1);ListNode* p = dumpHead;while (l1 && l2){if (l1->val < l2->val){p->next = l1;l1 = l1->next;}else{p->next = l2;l2=l2->next;}p = p->next;}while (l1){p->next = l1;l1 = l1->next;p = p->next;}while (l2){p->next = l2;l2 = l2->next;p = p->next;}return dumpHead->next;}};