数据结构之单链表

单向链表，大致操作有插入，删除，遍历，查找，销毁，它存取方便，只要修改节点的指针域即可。只是查找时，每次都需要从第一个开始遍历查找。

第一个节点只有直接后继，最后一个节点只有直接前驱。

对于插入操作，有头插法，尾插法，任意插，这些我们在实际运用中都要考虑到。它的一优势就是节省空间，灵活。而顺序表就容易造成空间的浪费。插入删除操作还会造成大量数据的移动。

单链表其实我认为是一种更为实用的数据类型，它将各种类型封装起来，来解决生活工作中遇到的实际问题。

下面开始实战：

/* list.h 头文件的定义 */

#ifndef _LIST_H_#define _LIST_H_#include <assert.h>typedef struct node{    int data;    struct node *next;}node_t;node_t *list_insert_fornt(node_t *head,int data);typedef  void (*FUNC)(node_t *);void list_for_each(node_t *head,FUNC f);node_t *list_get_node(node_t *head,int index);node_t *list_insert_at(node_t *head,int data,int index);node_t *list_remove_at(node_t *head,int index);node_t *list_find(node_t *head,int data,int *ret);node_t *list_free(node_t *head,int data);#endif  /* _LIST_H_ */

/* list.c    接口的实现 */

#include "list.h"#include <stdio.h>node_t *list_insert_fornt(node_t *head,int data){    node_t *n = (node_t *)malloc(sizeof(node_t));    assert(n != NULL);    n->data  = data;    n->next = NULL;    if(head == NULL)        head = n;    else    {        n->next = head;        head = n;    }    return head;}

void  *list_for_each(node_t *head,FUNC f){    while(head)    {        f(head);        head = head->next;    }}node_t *list_get_node(node_t *head,int index){    int j = 0;    while(head && j < index)    {        head = head->next;        j++;    }    if(j == index)

<span style="white-space:pre"></span>return head;    return NULL;   //return head;}node_t *list_insert_at(node_t *head,int data,int index){    if(index == 0)    return list_insert_front(head,data);    node_t *n = (node_t *)malloc(sizeof(node_t));    assert(n != NULL);    n->data = data;    n->next = NULL;    node_t *p = NULL;    p = list_get_node(head,index - 1);    if(p != NULL)    {        n->next = p-next;        p->next = n;    }    else        printf("insert error.\n");    return head;}node_t *list_remove_at(node_t *head,int index){    assert(index >= 0);    if(index == 0)    {        n = head;        free(n);         head = head->next;    }    node_t *p = NULL;    p = list_get_node(head,index -1);    if(p == NULL || p->next == NULL)    {        fprintf(stderr,"remove error.\n");        exit(EXIT_FAILURE);    }    n = p->next;    p->next = n->next;    return head;}node_t *list_find(node_t *head,int data,int *ret){    *ret = -1;    int i = 0;    while(head)    {        if(data == head->data)        {            *ret = i;            break;        }        head = head->next;        i++;    }    return head;}node_t *list_free(head,data){    node_t *tmp = head;    while(head)    {        head =head->next;        free(tmp);        tmp = head;    }    return head;}

/* main.c  测试代码  */

#include "list.h"#include <stdio.h>void print_node(node_t *n){    printf("data = %d \n",n->data);}int main(void){    node_t *head = NULL;    head = list_insert_fornt(head,30);    head = list_inset_fornt(head,20);    head = list_insert_fornt(head,10);    list_for_each(head,print_node);    putchar('\n');    node_t *n = NULL;    n = list_get_node(head,1);    if(n != NULL)        printf("data = %d\n",n->data);    else        printf("not find node.\n");    head = list_insert_at(head,15,1);    list_for_each(head,print_node);    putchar('\n');    head = list_remove_at(head,2);    list_for_each(head,print_node);    putchar('\n');    node_t *n = NULL;    int ret = 0;    n = list_find(head,20,&ret);    if(n != NULL)        printf("data = %d index = %d \n",n->data,ret);    else        printf("not find.\n");    head =list_free(head,data);    assert(head == NULL);    return 0;}

以下是运行示例：分别是插入，查找，任意插入，删除节点，找出节点，最后销毁链表。

(finish)