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.

新建一个链表，然后比较两个链表中的元素值，把较小的那个链到新链表中，由于两个输入链表的长度可能不同，所以最终会有一个链表先完成插入所有元素，则直接另一个未完成的链表直接链入新链表的末尾.

需要 dummy记录原始表头

class Solution(object):
    def mergeTwoLists(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        dummy = cur = ListNode(0)
        while l1 and l2:
            if l1.val < l2.val:
                cur.next = l1
                l1 = l1.next
            else:
                cur.next = l2
                l2= l2.next
            cur = cur.next
        cur.next = l1 or l2
        return dummy.next

二刷：

记住将另一个未完成的链表直接链入新链表的末尾python的表达方式

cur.next = l1 or l2