"""
将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。
示例:
输入:1->2->4, 1->3->4
输出:1->1->2->3->4->4
"""
链表结构:
class ListNode():
def __init__(self, x):
self.val = x
self.next = None
class Solution:
# 方法一 :
def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
head = ListNode(None)
l3 = head
while l1 and l2 :
if l1.val < l2.val:
# 重点: 时刻保持下一个 .next 结构是一个 ListNode
l3.next = ListNode(l1.val)
l1 = l1.next
else:
l3.next = ListNode(l2.val)
l2 = l2.next
l3 = l3.next
if l1 == None:
while l2:
l3.next = ListNode(l2.val)
l3 = l3.next
l2 = l2.next
else:
while l1:
l3.next = ListNode(l1.val)
l3 = l3.next
l1 = l1.next
return head.next
# 方法 二
def mergeTwoLists2(self, l1: ListNode, l2: ListNode) -> ListNode:
# 递归解法
if not l1: return l2
if not l2: return l1
if l1.val < l2.val:
l1.next = self.mergeTwoLists(l1.next, l2)
return l1
else:
l2.next = self.mergeTwoLists(l1, l2.next)
return l2
验证,设置输入、输出:
if __name__ == "__main__":
s = Solution()
#输入: 1->2->4
# 1->3->4
# 输出:1->1->2->3->4->4
l1 = ListNode(1)
tmp = ListNode(2)
l1.next = tmp
tmp.next = ListNode(4)
l2 = ListNode(1)
tmp = ListNode(3)
l2.next = tmp
tmp.next = ListNode(4)
r = s.mergeTwoLists2(l1,l2)
print(r.val)
# 先判断是否为 None , 再去打印
while r.next != None:
r = r.next
print(r.val)