21. 合并两个有序链表

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/merge-two-sorted-lists
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

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    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {

        ListNode list1 = l1;
        ListNode list2 = l2;
        ListNode head = new ListNode();
        ListNode cur = head;
        while(list1 != null && list2 != null) {
            if(list1.val < list2.val) {
                cur.next = list1;
                list1 = list1.next;
            } else {
                cur.next = list2;
                list2 = list2.next;
            }
            cur = cur.next;
        }

        if(list1!= null) {
            cur.next = list1;
        }

        if(list2!=null) {
            cur.next = list2;
        }

        return head.next;

    }