题解 | #牛牛的链表交换#

#include <stdio.h>
#include <stdlib.h>

typedef struct node{
    int data;
    struct node *next;
}node;

//创建头节点
node *add_head()
{
    node *Head = malloc(sizeof(node));
    if (Head == NULL) {
        printf("out of memory");
        exit(1);
    }
    Head->next = Head;
    return Head;
}

void add_node(node *Head, int data)
{
    node *new = malloc(sizeof(node));
    if (new == NULL) {
        exit(1);
    }
    new->data = data;
    new->next = NULL;

    node *pT = NULL;
    pT = Head; 
  if(pT->next != Head) 
		pT = pT->next;

    new->next = pT->next;
    pT->next = new;
}

//节点交换
void swap_node(node *Head)
{
    node *p1 = Head->next;
    node *p2 = Head->next->next;
    //前两个节点交换
    p1->next = p2->next;
    p2->next = p1;
    Head->next = p2;

    node *pT = NULL;
    node *pT1 = NULL;
    node *pT2 = NULL;
    for (pT = Head; pT->next->next->next != Head; pT = pT->next);
    for (pT1 = Head; pT1->next->next != Head; pT1 = pT1->next);
    for (pT2 = Head; pT2->next != Head; pT2 = pT2->next);
    //后两个节点交换
    pT1->next = Head;
    pT2->next = pT1;
    pT->next = pT2;
}
//输出链表
void output(node *Head)
{
    if (Head->next == Head) {
        return;
    }
    node *pT = Head->next;
    while (pT != Head) {
        printf("%d ", pT->data);
        pT = pT->next;
    }
}

int main() {
    node *Head = add_head();//返回头节点的地址给头指针
    int n;
    scanf("%d",&n);
    int arr[n];
    for (int i = 0; i < n; i++) {
        scanf("%d",&arr[i]);
    }
    //将数据插入链表
    for (int j = 0; j < n; j++) {
        add_node(Head, arr[j]);
    }
    swap_node(Head);
    output(Head);
    return 0;
}