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最新推荐文章于 2025-05-22 22:16:20 发布

张沙包

最新推荐文章于 2025-05-22 22:16:20 发布

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CC 4.0 BY-SA版权

本文链接：https://blog.youkuaiyun.com/weixin_43201010/article/details/99657741

本文介绍了一种在O(nlogn)时间复杂度和常数级空间复杂度下对链表进行排序的方法。通过快慢指针找到中点，将链表分为两半，递归排序后合并两个有序链表。

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在 O(n log n) 时间复杂度和常数级空间复杂度下，对链表进行排序。

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def sortList(self, head: ListNode) -> ListNode:
        if not head or not head.next: return head
        pre, slow, fast = head, head, head
        while fast and fast.next:
            pre = slow
            slow = slow.next
            fast = fast.next.next
        pre.next = None
        l1 = self.sortList(head)
        l2 = self.sortList(slow)
        return self.mergeTwoLists(l1, l2)
    
    def mergeTwoLists(self, l1, l2):
        head = ListNode(0)
        move = head
        if not l1: return l2
        if not l2: return l1
        while l1 and l2:
            if l1.val < l2.val:
                move.next = l1
                l1 = l1.next
            else:
                move.next = l2
                l2 = l2.next
            move = move.next
        move.next = l1 if l1 else l2
        return head.next