# 链表

翻转链表方法

#include <iostream>
#include <algorithm>

using namespace std;

struct List{
    List *next;
    int val;
};


void Creat(List* head,int n){
    List *p=head;
    for(int i=1;i<=n;i++){
        List *tmp=new List;
        tmp->val=i;
        tmp->next= nullptr;
        p->next=tmp;
        p=p->next;
    }
}

void traver(List* head){
    List* tmp=head->next;
    while (tmp!= nullptr){
        cout<<tmp->val<<" ";
        tmp=tmp->next;
    }
    cout<<endl;
}

List* test(List* head,int k){
    List* end=head->next;
    while(end->next!= nullptr){
        end=end->next;
    }
    end->next=head->next;   //把链表变成环，尾节点接到头节点
    List *tmp=end->next;

    //循环到需要更改到节点前一个
    for(int i=0;i<k-1;i++){
        tmp=tmp->next;
    }
    //把下一个节点作为头节点，并赋值
    List *ans=new List;
    ans->next=tmp->next;

    //把下一个节点的next指针改为null
    tmp->next= nullptr;
    return ans;
}


int main() {
    List *head=new List;
    Creat(head,5);

    traver(test(head,3));

}

package main

import "fmt"

type ListNode struct {

	Next *ListNode

	Val  int

}

func InitList(head *ListNode, n int) {

	tmp := head

	for i := 1; i <= n; i++ {

		res := new(ListNode)

		res.Val = i

		res.Next = nil

		tmp.Next = res

		tmp = tmp.Next

	}

}

func Show(head *ListNode) {

	tmp := head.Next

	for tmp != nil {

		fmt.Println(tmp.Val)

		tmp = tmp.Next

	}

}

func Reversal(head *ListNode, k int) *ListNode {

	tmp := head.Next

	for tmp.Next != nil {

		tmp = tmp.Next

	}

	tmp.Next = head.Next

	res := tmp.Next

	for i := 0; i < k-1; i++ {

		res = res.Next

	}

	ans := new(ListNode)

	ans.Next = res.Next

	res.Next = nil

	return ans

}

func main() {

	head := new(ListNode)

	InitList(head, 5)

	Show(Reversal(head, 3))

}