​2021-03-17：手写代码：单链表插入排序。

package main

import "fmt"

func main() {
    //head := &ListNode{Val: 4}
    //head.Next = &ListNode{Val: 2}
    //head.Next.Next = &ListNode{Val: 1}
    //head.Next.Next.Next = &ListNode{Val: 3}

    head := &ListNode{Val: -1}
    head.Next = &ListNode{Val: 5}
    head.Next.Next = &ListNode{Val: 3}
    head.Next.Next.Next = &ListNode{Val: 4}
    head.Next.Next.Next.Next = &ListNode{Val: 0}

    printlnLinkNodeList(head)

    head = InsertSort(head)

    printlnLinkNodeList(head)
}

//Definition for singly-linked list.
type ListNode struct {
    Val  int
    Next *ListNode
}

//链表打印
func printlnLinkNodeList(head *ListNode) {
    cur := head
    for cur != nil {
        fmt.Print(cur.Val, "\t")
        cur = cur.Next
    }
    fmt.Println()
}

//插入排序
func InsertSort(head *ListNode) *ListNode {
    if head == nil || head.Next == nil {
        return head
    }
    preAns := &ListNode{Next: head}

    pre := head
    cur := head.Next
    for cur != nil {
        if pre.Val <= cur.Val {
            //不管

            //下一个循环的准备工作
            pre, cur = cur, cur.Next
        } else {
            preTemp := preAns
            temp := preAns.Next
            for cur.Val >= temp.Val {
                preTemp, temp = temp, temp.Next
            }

            //删除当前节点
            pre.Next = cur.Next

            //有序节点里插入当前节点
            preTemp.Next, cur.Next = cur, temp

            //下一个循环的准备工作，pre不变
            cur = pre.Next
        }

    }
    return preAns.Next
}