Solution
from typing import Optional
class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
class Solution:
def mergeTwoLists(
self, list1: Optional[ListNode], list2: Optional[ListNode]
) -> Optional[ListNode]:
dummy = ListNode()
curr = dummy
while list1 and list2:
if list1.val <= list2.val:
curr.next = list1
list1 = list1.next
else:
curr.next = list2
list2 = list2.next
curr = curr.next
curr.next = list1 or list2
return dummy.next
# 本地测试工具
def build(arr):
if not arr:
return None
head = ListNode(arr[0])
p = head
for v in arr[1:]:
p.next = ListNode(v)
p = p.next
return head
def show(node):
res = []
while node:
res.append(str(node.val))
node = node.next
print(f"[{','.join(res)}]")
if __name__ == "__main__":
sol = Solution()
l1 = build([1,2,4])
l2 = build([1,3,4])
show(sol.mergeTwoLists(l1, l2)) # [1,1,2,3,4,4]
show(sol.mergeTwoLists(build([]), build([]))) # []
show(sol.mergeTwoLists(build([]), build([0]))) # [0]