LeetCode 21 Merge Two Sorted Lists

// Author : yqtao
// Date   : 2016-7-3
// Email  : [email protected]
/**********************************************************************************
* * 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) {}
* };
*/

ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) {
 ListNode dummy(INT_MIN);
 ListNode *tail = &dummy;

 while (l1 && l2) {
 if (l1->val < l2->val) {
 tail->next = l1;
 l1 = l1->next;
 }
 else {
 tail->next = l2;
 l2 = l2->next;
 }
 tail = tail->next;
 }

 tail->next = l1 ? l1 : l2;
 return dummy.next;
}