merge_sorted_list
merge_sorted_list.py 源码
# 合并两个有序链表
# https://leetcode-cn.com/problems/merge-two-sorted-lists/solution
class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
class Solution:
# 迭代
def mergeTwoLists_1(self, l1: ListNode, l2: ListNode) -> ListNode:
dummy = ListNode(-1)
p = dummy
while l1 and l2:
if l1.val < l2.val:
p.next = l1
l1 = l1.next
else:
p.next = l2
l2 = l2.next
p = p.next
p.next = l1 if l1 else l2
return dummy.next
# 递归
def mergeTwoLists_2(self, l1: ListNode, l2: ListNode) -> ListNode:
def helper(p, node1, node2):
if not node1 or not node2:
p.next = node1 if node1 else node2
return
if node1.val < node2.val:
p.next = node1
helper(p.next, node1.next, node2)
else:
p.next = node2
helper(p.next, node1, node2.next)
dummy = ListNode(-1)
p = dummy
helper(p, l1, l2)
return dummy.next
# 高票答案的递归写法，学习一下
def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
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
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