LeetCode-Easy部分中标签为LinkedList 21. Merge Two Sorted Lists

原题

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.

题目分析

合并两个有序链表。运用归并排序的合并思想。

代码实现

public ListNode MergeTwoLists(ListNode l1, ListNode l2)
        {
            if (l1 == null) return l2;
            if (l2 == null) return l1;

            ListNode merge;
            //首先确定merge的头节点指向谁
            if (l1.val < l2.val)
            {
                merge = l1;
                l1 = l1.next;
            }
            else
            {
                merge = l2;
                l2 = l2.next;
            }

            ListNode im = merge; //临时指针指向merge
            while (l1 != null)
            {
                if (l2 != null)
                {
                    if (l1.val < l2.val)
                    {
                        im.next = l1;
                        l1 = l1.next;
                    }
                    else
                    {
                        im.next = l2;
                        l2 = l2.next;
                    }
                    im = im.next;
                }
                else //b首先等于null
                {
                    im.next = l1;
                    break;
                }
            }

            if (l2 != null) //a首先等于null
                im.next = l2;

            return merge;

        }

更多LinkList题目

http://blog.youkuaiyun.com/daigualu/article/details/69077428