LeetCode21Merge Two Sorted Lists

// Author : yqtao// Date   : 2016-7-3// Email  : [e-mail]/************************************************************************************ 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;}