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.

题目描述：

类似以前C语言做的输入两个链表，按照顺序大小将其连接。

不过这次试着用JAVA做，思路还是一样。

代码：

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode head;
        if(l1==null) //判断是否有一个串是空串
            return l2;
        else if(l2==null)
            return l1;

        if(l1.val<l2.val){ //判断第一个结点
            head = l1;
            l1=l1.next;
        }
        else{
            head = l2;
            l2=l2.next;
        }
        ListNode temp = head;
        while(l1!=null&&l2!=null)
        {
            if(l1.val<l2.val)//比较每一个结点
            {
                temp.next = l1;
                temp=temp.next;
                l1 = l1.next;
            }
            else
            {
                temp.next = l2;
                temp=temp.next;
                l2 = l2.next;
            }
        }
        if(l1==null) //一个串结束直接接上另外一个
            temp.next=l2;
        else
            temp.next = l1;
        return head;
    }
}

LeetCode Merge Two Sorted Lists