Task7: merging two ordered lists

topic

The two ordered lists into a new sorted list and return. The new list is by all nodes in a given mosaic composed of two lists.

Problem-solving

class Solution:
    def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
        prehead = ListNode(-1)

        prev = prehead
        while l1 and l2:
            if l1.val <= l2.val:
                prev.next = l1
                l1 = l1.next
            else:
                prev.next = l2
                l2 = l2.next            
            prev = prev.next

        # exactly one of l1 and l2 can be non-null at this point, so connect
        # the non-null list to the end of the merged list.
        prev.next = l1 if l1 is not None else l2

        return prehead.next

Author: LeetCode
link: https: //leetcode-cn.com/problems/merge-two-sorted-lists/solution/he-bing-liang-ge-you-xu-lian-biao-by-leetcode/
Source: force buckle (LeetCode)
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