Nailer's blog

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
        if not l1:
            return l2
        if not l2:
            return l1
        head = comp = None
        if l1.val <= l2.val:
            head, comp = l1, l2
        else:
            head, comp = l2, l1
        gateway = head
        while head and comp:
            if not head.next:
                head.next = comp
                return init
            if head.next.val < comp.val:
                head = head.next
                continue
            if head.next.val >= comp.val:
                tmp = comp
                comp = comp.next
                tmp.next = head.next
                head.next = tmp
                head = tmp
        return gateway