C语言实现双向链表

这个小代码是我凭自己对指针和链表的理解和认识，自己实现的，没有参考其他人的代码，如果有相同的地方，那真的只是巧合，代码我在ubuntu 15.04下测试通过，可能存在很多错误和漏洞．

doublelist.c

/*************************************************************************
  > File Name: doublelist.c
  > Author: ChenYiLiang
  > Mail: [e-mail]
  > Created Time: Sat 21 Mar 2015 07:32:22 PM CST
 ************************************************************************/

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

struct userdata{
  int userid;
  char username[30];

  struct userdata *previous;
  struct userdata *next;
};



struct userdata *header;
size_t scanf_id;
char scanf_name[30];

int yesno;
int deletePosition;
int alterPosition;
int alterId;
char alterName[30];

int searchPosition;

FILE *ptr_fpid;

/*向链表中插入数据*/
int insert_list(struct userdata *header, size_t position, char name[], size_t id);
/*删除链表中指定的节点*/
int delete_node(struct userdata *header, size_t position);
/*修改指定位置的节点信息*/
int alter_node(struct userdata *header, size_t position, size_t id, char name[]);
/*查找链表中的数据*/
struct userdata *search_node(struct userdata *header, size_t position);
/*遍历链表*/
int travel_list(struct userdata *header);
/*判断链表是空*/
int isempty(struct userdata *header);

/*将链表结构写入文件*/
int write_into_file(struct userdata *header, FILE *fp);
/*从文件读取数据放到链表中*/
int read_from_file(struct userdata *header, FILE *fp);

int main(){
  struct userdata *header_node = (struct userdata *)malloc(sizeof(struct userdata));
  header_node -> previous = NULL;
  header_node -> next = NULL;

  read_from_file(header_node, ptr_fpid);
  travel_list(header_node);
  while(1){
  //scanf("%*[^\n]");
  //scanf("%*c");
  //scanf("%*[^\n]");
  printf("please input id - ");
  scanf("%d", &scanf_id);
  //scanf("%*c");
  //scanf("%*[^\n]");
  printf("please input your name - ");
  scanf("%s", scanf_name);

  printf("%d - %s\n\n", scanf_id, scanf_name);

  //isempty(header_node);

  /*0表示默认插入到链表的尾部*/
  insert_list(header_node, 0, scanf_name, scanf_id);

  //write_into_file(header_node, ptr_fpid);
  //isempty(header_node);


    printf("input anymore - ");
    scanf("%d", &yesno);
    if(yesno == -1){
      break;
    }

  scanf("%*c");
  scanf("%*[^\n]");
// travel_list(header_node);

  }
  getchar();
  //printf("delete position data - ");
  //scanf("%d", &deletePosition);
  //delete_node(header_node, deletePosition);

// printf("alter data for position - ");
// scanf("%d", &alterPosition);
// printf("please inout new id - ");
// scanf("%d",&alterId);
// printf("please input new name - ");
// scanf("%s", alterName);
// alter_node(header_node, alterPosition, alterId, alterName);
  write_into_file(header_node, ptr_fpid);
  travel_list(header_node);
  printf("\n\n");
  printf("please input position to search - ");
  scanf("%d", &searchPosition);
  struct userdata *searchData = search_node(header_node, searchPosition);
  printf("%d\n", searchData -> userid);
  printf("%s\n", searchData -> username);
  return 0;
}

/* 插入节点 */
int insert_list(struct userdata *header, size_t position, char name[], size_t id ){
  struct userdata *temp_newuser = header;
  struct userdata *getMemory = (struct userdata *)malloc(sizeof(struct userdata));

  getMemory -> userid = id;
  strncpy(getMemory -> username, name, 30);
  /*当position == 0时,表示默认插入到链表的尾部*/
  if(0 == position){
    if(NULL != temp_newuser -> next){
      while(NULL != temp_newuser -> next){
        temp_newuser = temp_newuser -> next;
      }
    }
  }

  /*当position > 1时则寻找合适的位置插入*/
  if(1 <= position){
    for(int i = 0; i <= position; i++){
      /*当执行此处的代码时表示,链表已经到达尾部或者是空链表*/
      if(NULL == temp_newuser -> next){
        break;
      }
      temp_newuser = temp_newuser -> next;
    }
  }

  getMemory -> previous = temp_newuser;
  if(temp_newuser -> next == NULL){
    temp_newuser -> next = getMemory;
    getMemory -> next = NULL;
  }else{
    temp_newuser -> next -> previous = getMemory;
    getMemory -> next = temp_newuser -> next;
    temp_newuser -> next = getMemory;
  }

  return 0;
}

/*删除链表中指定的节点*/
int delete_node(struct userdata *header, size_t position){
  int is_empty = isempty(header);
  if(0 == is_empty){
    printf("this si a empty list!\n\n");
    return -1;
  }

  struct userdata *deleteNode = header;

    for(int i = 0; i < position; i++ ){
      /*当执行此处的代码时表示,链表已经到达尾部或者是空链表*/
      if(NULL == deleteNode -> next){
        break;
      }
      deleteNode = deleteNode -> next;
    }

  /**/
  deleteNode -> next -> previous = deleteNode -> previous;
  deleteNode -> previous -> next = deleteNode -> next;
  free(deleteNode);

  return 0;
}

/*修改指定位置的节点信息*/
int alter_node(struct userdata *header, size_t position, size_t id, char name[]){
  int isEmpty = isempty(header);
  if(0 == isEmpty){
    printf("this is a empty list\n\n");
    return -1;
  }

  struct userdata *alterNode = header;
    for(int i = 0; i < position; i++ ){
      /*当执行此处的代码时表示,链表已经到达尾部或者是空链表*/
      if(NULL == alterNode -> next){
        break;
      }
      alterNode = alterNode -> next;
    }

    alterNode -> userid = id;
    strncpy(alterNode -> username, name, 30);

  return 0;
}

/*查找链表中的数据*/
struct userdata *search_node(struct userdata *header, size_t position){
  int isEmpty = isempty(header);
  if(0 == isEmpty){
    printf("this is a empty!\n");
    return NULL;
  }

  struct userdata *searchNode = header;
  for(int i = 0; i < position; i++){
    if(NULL == searchNode -> next){
      break;
    }
    searchNode = searchNode -> next;
  }

  return searchNode;
}

/*遍历链表*/
int travel_list(struct userdata *header){
  struct userdata *travel = header;
  if(NULL == travel -> next){
    printf("This is a empty list!!\n");
    return 1;
  }

  for(travel = travel -> next ; ; travel = travel -> next){
    printf("%d\n",travel -> userid);
    printf("%s\n", travel -> username);
    if(NULL == travel -> next){
      break;
    }
  }

  return 1;
}

/*判断链表是空*/
int isempty(struct userdata *header){
  if(header -> next == NULL){
    return 0;
  }else{
    return 1;
  }
}

/*将链表结构写入文件*/
int write_into_file(struct userdata *header, FILE *fp){
  fp = fopen("listdata", "wb");
  if(NULL == fp){
    perror("open file failed when write into file!"),exit(-1);
  }

  printf("come into write!\n");
  for(struct userdata *move = header -> next; ; move = move -> next){
    fwrite(move,sizeof(struct userdata), 1, fp);
    if(NULL == move -> next){
      break;
    }
  }
  fclose(fp);
  fp = NULL;
  return 0;
}
/*从文件读取数据放到链表中*/
int read_from_file(struct userdata *header, FILE *fp){
  struct userdata *readfile = header;
  fp = fopen("listdata", "rb");
  if(NULL == fp){
    perror("open file failed when read - ");
    return -1;
  }

  while(1){
    struct userdata *newread = (struct userdata *)malloc(sizeof(struct userdata));
    fread(newread, sizeof(struct userdata), 1, fp);
    if(feof(fp)){/*当读取到文件的尾部时．跳出循环*/
      break;
    }
    readfile -> next = newread;
    newread -> next = NULL;
    newread -> previous = readfile;
    readfile = newread;
  }
  fclose(fp);
  fp = NULL;
  return 0;
}

C语言实现双向链表删除节点、插入节点、双向输出等操作

#include<cstdio>
#include<cstdlib>
typedef struct DoubleLinkedList
{
  int data;
  struct DoubleLinkedList *pre;
  struct DoubleLinkedList *next;
}DlinkedList_Node;
//建立链表
DlinkedList_Node* createDLink()
{
  DlinkedList_Node *head,*p,*s;
  int x;
  head = (DlinkedList_Node*)malloc(sizeof(DlinkedList_Node));
  p = head;
  while(1)
  {
    printf("please input the data: \n");
    scanf("%d",&x);
    if(x != 65535)
    {
      s = (DlinkedList_Node*)malloc(sizeof(DlinkedList_Node));
      s ->data = x;
      s-> pre = p;
      p->next = s;
      p=s;
    }
    else
      {
        printf("\n数据输入结束\n");
        break;
      }
  }
  p->next = NULL;
  head = head ->next;
  head->pre = NULL;
  return head;
}
//顺序、反序打印链表
void printDLink(DlinkedList_Node *head)
{
  DlinkedList_Node *p,*s;
  p = head;
  printf("正序输出双向链表：\n");
  while(p)
  {
    printf("%d ",p->data);
    s = p;
    p = p->next;
  }
  printf("\n 逆序输出双向链表: \n");
  while(s)
  {
    printf("%d ",s->data);
    s = s->pre;
  }
  printf("\n \n");
}
//删除一个结点
DlinkedList_Node* deleteDlinkedList_Node(DlinkedList_Node *head,int i)
{
  DlinkedList_Node *p;
  p = head;
  if(p->data == i)
  {
    head = p->next;
    head->pre = NULL;
    free(p);
    return head;
  }
  while(p)
  {
    if(p->data == i)
    {
    p->pre->next = p->next;
    p->next->pre = p->pre;
    free(p);
    return head;
    }
    p = p->next;
  }
  printf("没有找到想要删除的数据\n");
  return head;
}
//插入一个结点
DlinkedList_Node* insertDlinkedList_Node(DlinkedList_Node *head,int i)
{
  DlinkedList_Node *p,*temp;
  p = head;
  temp = (DlinkedList_Node*)malloc(sizeof(DlinkedList_Node));
  temp ->data = i;
  if(i < p->data)//比头结点数据小，插入到链表头部
  {
    head = temp;
    head->next = p;//此处p为原来的head
    head->pre = NULL;
    p->pre = head;//此处p为原来的head
    return head;
  }
  while(p != NULL && i > p->data)//寻找合适的插入位置
  {
    p = p->next;
  }
  if(i < p->data)//在链表中间某处找到合适插入位置
  {
    temp ->next = p;
    temp ->pre = p->pre;
    p ->pre->next = temp;
    p ->pre = temp;
    return head;
  }
  else//没有找到合适的位置，只有将数据插入到链表尾部
  {
    p->next = temp; //遍历到链表尾部，p==NULL
    temp ->pre = p;
    temp ->next = NULL;
    return head;
  }
}
int main()
{
  DlinkedList_Node *head;
  head = createDLink();
  printDLink(head);
  head = insertDlinkedList_Node(head,1012);
  head = deleteDlinkedList_Node(head,1991);
  printDLink(head);
}
/*****************************
运行结果如下：
please input the data:
1991
please input the data:
1992
please input the data:
2013
please input the data:
2014
please input the data:
512
please input the data:
420
please input the data:
65535

数据输入结束
正序输出双向链表：
1991 1992 2013 2014 512 420
 逆序输出双向链表:
420 512 2014 2013 1992 1991

正序输出双向链表：
1012 1992 2013 2014 512 420
 逆序输出双向链表:
420 512 2014 2013 1992 1012

******************************/

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