leetcode -- 排序

题目1 .链表合起来（单链表使用归并，双向链表用快排）

https://leetcode.com/problems/merge-two-sorted-lists/

题目简介： 把两个有序链表合起来

题解：略

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        if(l1 == null || l2 ==null)return l1 ==null?l2:l1;
        ListNode head = new ListNode(-1);
        ListNode temp = head;
        while(l1 !=null && l2 != null){
            if(l1.val < l2 .val){
                temp.next = l1;
                l1 = l1.next;
            }else{
                temp.next = l2;
                l2 = l2.next;
            }
            temp = temp.next;
            temp.next = null;
        }
        temp.next = l1==null ?l2:l1;
        return head.next;
    }
}