合并两个排序的链表

输入两个递增排序的链表，合并这两个链表并使新链表中的节点仍然是递增排序的。

示例1：

输入：1->2->4, 1->3->4 输出：1->1->2->3->4->4

限制：

0 <= 链表长度 <= 1000

class P剑指 Offer 25HeBingLiangGePaiXuDeLianBiaoLcof{
public static void main(String[]args){
        Solution solution=new P剑指 Offer 25HeBingLiangGePaiXuDeLianBiaoLcof().new Solution();
        }
//leetcode submit region begin(Prohibit modification and deletion)

/**
 * Definition for singly-linked list.
 * public class ListNode {
 * int val;
 * ListNode next;
 * ListNode(int x) { val = x; }
 * }
 */
class ListNode {
    int val;
    ListNode next;

    ListNode(int x) {
        val = x;
    }
}

class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode dum = new ListNode(0), cur = dum;
        while(l1 != null && l2 != null) {
            if(l1.val < l2.val) {
                cur.next = l1;
                l1 = l1.next;
            }
            else {
                cur.next = l2;
                l2 = l2.next;
            }
            cur = cur.next;
        }
        cur.next = l1 != null ? l1 : l2;
        return dum.next;//dum指向的只是虚拟头节点
    }
}
//leetcode submit region end(Prohibit modification and deletion)

}