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| // @Title: 排序链表 (Sort List)
// @Author: 15816537946@163.com
// @Date: 2019-11-07 18:31:54
// @Runtime: 8 ms
// @Memory: 4.9 MB
/*
* @lc app=leetcode.cn id=148 lang=golang
*
* [148] 排序链表
*
* https://leetcode-cn.com/problems/sort-list/description/
*
* algorithms
* Medium (61.57%)
* Likes: 256
* Dislikes: 0
* Total Accepted: 21.2K
* Total Submissions: 34.3K
* Testcase Example: '[4,2,1,3]'
*
* 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。
*
* 示例 1:
*
* 输入: 4->2->1->3
* 输出: 1->2->3->4
*
*
* 示例 2:
*
* 输入: -1->5->3->4->0
* 输出: -1->0->3->4->5
*
*/
/**
* Definition for singly-linked list.
* type ListNode struct {
* Val int
* Next *ListNode
* }
*/
// 归并排序
func sortList(head *ListNode) *ListNode {
if head == nil || head.Next == nil {
return head
}
slow := head
fast := head.Next
for fast != nil && fast.Next != nil {
slow, fast = slow.Next, fast.Next.Next
}
// 1. 断链
mid := slow.Next
slow.Next = nil
// 2. 切割
left := sortList(head)
right := sortList(mid)
header := new(ListNode)
cursor := header
// 3. 合并
for left != nil && right != nil {
if left.Val > right.Val {
cursor.Next, right = right, right.Next
} else {
cursor.Next, left = left, left.Next
}
cursor = cursor.Next
}
if left != nil {
cursor.Next = left
} else {
cursor.Next = right
}
return header.Next
}
|