[LeetCode-Java]21. Merge Two Sorted Lists

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.

解：链表的基本操作。

public class Solution {    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        ListNode head = null;        ListNode temp = null;//存放已排序部分的最后一个位置             if (l1 == null) return l2;        if (l2 == null) return l1;        if (l1.val <= l2.val){            head = l1;        }else {            head = l2;        }        //比较移动l1和l2        while (l1!= null && l2 != null){            if (l1.val <= l2.val){                if (temp != null) temp.next = l1;                temp = l1;  //temp始终指向两者之中最小的那个                l1 = l1.next;            }else {                if (temp != null) temp.next = l2;                temp = l2;                l2 = l2.next;            }        }          if (l1 == null) temp.next = l2;        if (l2 == null) temp.next = l1;        return head;     }     }