leetcode 021 Merge Two Sorted Lists

题目

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.

思路：

简单题，利用链表的特点进行合并。

代码：

public ListNode mergeTwoLists(ListNode l1, ListNode l2)
{
if(l1 == null)
return l2;
else if(l2 == null)
return l1;
ListNode p1 = l1, p2 = l2;
ListNode p3, l3;
p3 = l3 = new ListNode(0);//注意这里，设一个头节点，方便操作
l3.next = l1;
while(p1 != null && p2 != null)
{
if(p1.val <= p2.val)
{
p3.next = p1;
p3 = p1;
p1 = p1.next;
} else
{
p3.next = p2;
p3 = p2;
p2 = p2.next;
}
}
p3.next = p1==null ? p2 : p1;
return l3.next; //因为我们设了一个头节点，所以要跳过头节点
}

结果细节（图）：