题解 | #合并两个排序的链表#

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode Merge(ListNode list1, ListNode list2) {
        if(list1==null && list2!=null){
           return list2;
        }
        else if(list1!=null && list2==null){
            return list1;
        }
       else if(list1==null && list2==null){
        return null;
       }
       ListNode l1=list1;

        ListNode l2=list2;
         ListNode temp = new ListNode(0);
        while (list1 != null && list2 != null) {

            if (list1.val <= list2.val) {
                temp.next = list1;
                list1 = list1.next;
                temp = temp.next;
            } else {
                temp.next = list2;
                list2 = list2.next;
                temp = temp.next;
            }

        }
        while (list1 != null) {
            temp.next = list1;
            list1 = list1.next;
            temp = temp.next;
        }

        while (list2 != null) {
            temp.next = list2;
            list2 = list2.next;
            temp = temp.next;
        }
        return l1.val<=l2.val?l1:l2;




    }

}

双指针，跟归并排序差不多