带头节点的单向链表（李慧芹视频案例）

李慧芹单项链表讲解视频：

https://www.bilibili.com/video/BV18p4y167Md?p=77

完整代码：

①list.h文件

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#ifndef LIST_H_
#define LIST_H_


typedef int datatype;

/* 定义节点*/
struct node_st
{
    datatype data;
    struct node_st* next;
};

/* 给节点的模板类型起别名为LIST_S */
typedef struct node_st LIST_S;

/*声明函数*/
LIST_S* list_create();
int list_insert_at(LIST_S*, int i, datatype*);
int list_order_insert(LIST_S*, datatype*);
int list_isempty(LIST_S*);
void list_display(LIST_S*);
void list_destroy(LIST_S*);

#endif

②list.c文件

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

#include "list.h"

/*创建带头节点的空链表*/
LIST_S* list_create()
{
    LIST_S* node;
    node = (LIST_S *)malloc(sizeof(*node));
    if (NULL == node)
    {
        return NULL;
    }
    node->next = NULL;

    return node;
}

/*删除链表*/
void list_destroy(LIST_S* me)
{
    LIST_S* node, * next;
    for (node = me->next; node != NULL; node = next)
    {
        next = node->next;
        free(node);
    }
    free(me);
    me = NULL;
    return;
}

/* 插入节点 */
int list_insert_at(LIST_S* me, int i, datatype *data)
{
    LIST_S* node = me;
    LIST_S* newnode;
    int j = 0;
    /*通过j的递增找到第i个节点*/
    while (j < i && NULL != node)
    {
        node = node->next;
    }

    /*如果第i个节点不为空，就新建一个节点插入到第i个节点的后面*/
    if (NULL != node)
    {
        newnode = (LIST_S *) malloc(sizeof(*newnode));
        if (NULL == newnode)
        {
            return -1;
        }
        newnode->data = *data;
        newnode->next = node->next;
        node->next = newnode;
    }
    else
    {
        return -1;
    }
    return 0;
}


/* 显示节点内容 */
void list_display(LIST_S* me)
{
    LIST_S* node = me->next;
    while (NULL != node)
    {
        printf("%d ", node->data);
        node = node->next;
    }
    return;
}
/* 判断链表是否为空链表 */
int list_isempty(LIST_S* me)
{
    if (NULL == me->next)
    {
        return 0;
    }
    return 1;
}


/* 按照从小到大的顺序插入节点 */
int list_order_insert(LIST_S* me, datatype* data)
{
    LIST_S* node = me;
    LIST_S* newnode;
    while (node->next && node->next->data < *data)
    {
        node = node->next;
    }

    newnode = (LIST_S *)malloc(sizeof(*newnode));
    if (NULL == newnode)
    {
        return -1;
    }

    newnode->data = *data;
    newnode->next = node->next;
    node->next = newnode;

    return 0;
}

③ main.c文件

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

#include "list.h"

int main()
{
    LIST_S* list;
    LIST_S* list1;
    datatype array[] = { 1,2,4,3,6,5,8,7,9};
    int num;
    int bIsempty;

    /* 首先创建带头结点的空链表*/
    list = list_create();
    if (NULL == list)
        return -1;
    else
    {
        printf("list create successful and is inserted at head as follows:\n");
    }

    /* 将数组元素作为节点data，新建新节点插入到链表上，插入位置为0*/
    for (num = 0; num < sizeof(array) / sizeof(array[0]); num++)
    {
        list_insert_at(list, 0, &array[num]);
    }


    /* 对链表是否为空进行判断，如果不为空就打印出链表来*/
    bIsempty = list_isempty(list);
    if (bIsempty == 1)
    {
        list_display(list);
    }
    printf("\n");


    /* 首先创建带头结点的空链表*/
    list1 = list_create();


    /* 按照从小到大的顺序插入节点*/
    for (num = 0; num < sizeof(array) / sizeof(array[0]); num++)
    {
        list_order_insert(list1, &array[num]);
    }

    /* 打印链表*/
    list_display(list1);

    /* 删除链表 */
    list_destroy(list);
    list_destroy(list1);
    return 0;
}

④ makefile 文件

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list: main.o list.o
        gcc main.o list.o -o list
main.o:main.c
        gcc main.c -c -Wall -g -o main.o
list.o:list.c
        gcc list.c -c -Wall -g -o list.o