暴力算法
python
# encoding = utf-8
# 开发者：Alen
# 开发时间： 10:51
# "Stay hungry，stay foolish."
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class ListNode(object):
def __init__(self, val=0, next=None):
self.val = val
self.next = next
class Solution(object):
def sortList(self, head):
"""
:type head: Optional[ListNode]
:rtype: Optional[ListNode]
"""
# Step 1: 提取所有值
cur = head
values = []
while cur:
values.append(cur.val)
cur = cur.next
# Step 2: 排序（注意：题目是排序链表，不是反转！）
values.sort() # 升序排序
# Step 3: 重建链表
dummy = ListNode(0) # 哑节点，方便操作
current = dummy
for val in values:
current.next = ListNode(val)
current = current.next
return dummy.next归并算法
大佬图示：
代码：
python
# encoding = utf-8
# 开发者：Alen
# 开发时间： 10:51
# "Stay hungry，stay foolish."
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class ListNode(object):
def __init__(self, val=0, next=None):
self.val = val
self.next = next
class Solution(object):
def sortList(self, head):
"""
:type head: Optional[ListNode]
:rtype: Optional[ListNode]
"""
if not head or not head.next:
return head
left = head
right = self.getMid(head)
tmp = right.next
right.next = None
right = tmp
left = self.sortList(left)
right = self.sortList(right)
return self.merge(left, right)
def getMid(self, head):
fast = head.next
slow = head
while fast and fast.next:
fast = fast.next.next
slow = slow.next
return slow
def merge(self, list1, list2):
tail = dummy = ListNode()
while list1 and list2:
if list1.val < list2.val:
tail.next = list1
list1 = list1.next
else:
tail.next = list2
list2 = list2.next
tail = tail.next
# 其中一个链为None，另一个可能不是None
if list1:
tail.next = list1
if list2:
tail.next = list2
return dummy.next结果
解题步骤：
