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.
思路：
由于链表是有序的，那么仅需要从两个链表的头开始比较即可。较小者插入新链表，然后向后依次比较。
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) { ListNode* dummy = new ListNode(0); ListNode* p = dummy ; while (l1 != NULL && l2 != NULL) { if (l1->val < l2->val) { p->next = l1; l1 = l1->next; } else { p->next = l2; l2 = l2->next; } p = p->next; } if (l1 != NULL)p->next = l1; if (l2 != NULL)p->next = l2; return dummy->next; }
[leetcode-21-Merge Two Sorted Lists]
原文：http://www.cnblogs.com/hellowooorld/p/6629353.html