数据结构（第二天）单链表的基本操作，创建单链表，头插法，尾插法，删除节点，查询节点

#include<stdio.h>#include<stdlib.h>typedef int DATATYPE;typedef struct node {    DATATYPE data;    struct node *next;}linklist;linklist *create_empty_linklist(){    linklist *head;    head = (linklist *)malloc(sizeof(linklist));    head->next = NULL;//当前创建出来的节点后续没有其他节点    return head;}int insert_data_by_head(linklist *head,DATATYPE data){    linklist *temp;    temp = (linklist *)malloc(sizeof(linklist));    temp->data = data;//  错误演示//  head->next = temp;//  temp->next = NULL;    temp->next = head->next;    head->next = temp;    return 0;}int insert_data_by_tail(linklist *head,DATATYPE data){    linklist *p = head;    linklist *temp;    while(p->next != NULL)        p = p->next;    temp = (linklist *)malloc(sizeof(linklist));    temp->data = data;    p->next = temp;    temp->next = NULL;    return 0;}int print_data(linklist *head){    linklist *p = head->next;//跳过头节点、头节点中没有数据    while(p != NULL)    {        printf("%d ",p->data);        p = p->next;    }    printf("\n");    return 0;}linklist *find_assign_data(linklist *head,DATATYPE data){    linklist *p = head->next;    while(p != NULL)    {        if(p->data != data)            p = p->next;        else             return p;    }}linklist *find_data_by_num(linklist *head,int num){    linklist *p = head;    int i = 1;    if(num == 0)        return head;    while(p->next != NULL)    {        if(i <= num)        {            p = p->next;            i ++;        }        else             return p;    }}int insert_data_anywhere(linklist *head,int post,DATATYPE data){    linklist *p;    linklist *temp;    p = find_data_by_num(head,post - 1);//目的是寻找post对应节点的前一个节点地址    temp = (linklist *)malloc(sizeof(linklist));    temp->data = data;    temp->next = p->next;    p->next = temp;    return 0;}int delete_assign_post_data(linklist *head,int post){    //要删除一个元素，必须先获取它的前面节点的地址    linklist *p;    p = find_data_by_num(head,post - 1);    linklist *temp;    if(p != NULL && p->next != NULL)    {        temp = p->next;        p->next = temp->next;        free(temp);        temp = NULL;    }    return 0;}void exchange_data(linklist *head){    linklist *p = head->next;    linklist *cur = p->next;        p->next = NULL;    while(cur != NULL)    {        p = cur->next;        cur->next = head->next;        head->next = cur;        cur = p;    }}void cleanup_linklist(linklist *head){    linklist *p = head;    linklist *temp;    while(p)    {        temp = p;        free(temp);        temp = NULL;        p = p->next;    }}int main(int argc, const char *argv[]){    linklist *head;    head = create_empty_linklist();    int i;    int data;    for(i = 0;i < 5;i ++)    {        scanf("%d",&data);//      insert_data_by_head(head,data);//头插法        insert_data_by_tail(head,data);//尾插法    }//  printf("%d\n",head->next->data);//  printf("%d\n",head->next->next->data);//  print_data(head);//  linklist *p;    //查找元素值为4的节点首地址//  p = find_assign_data(head,4);//  printf("%d\n",p->data);    //查找链表中第四个节点,头算第0个//  p = find_data_by_num(head,4);//  printf("%d\n",p->data);    //如何事先按照任意位置插入元素//  insert_data_anywhere(head,3,100);//在第三个位置插入元素100//  print_data(head);    //删除指定位置元素//  delete_assign_post_data(head,3);//删除第三个位置的元素    //  print_data(head);    exchange_data(head);    print_data(head);//  cleanup_linklist(head);//  print_data(head);    return 0;}