单链表基本操作实现——详解

      单链表是数据结构中十分常见，许多互联网公司笔试面试题好多都是单链表延伸出的，因此实能现一个单链表的基本操作很有必要，而且能让它不出现Bug还需要更细心。

基本功能：
1.添加元素            2.头插元素           
3.尾插元素            4.头删元素
5.尾删元素            6.销毁链表           
7.删除指定元素      8.指定位置插入元素

代码如下：#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<Windows.h>
#include<assert.h>
typedef int DataType;
typedef struct Slist
{
struct Slist *next;
DataType data;
}Slist;

Slist List;

Slist *BuySlist(DataType x) //添加元素
{
Slist *node = (Slist *)malloc(sizeof(Slist));
assert(node);
node->data = x;
node->next = NULL;
return node;
}

void ListPushback(Slist **head, DataType x) //尾插元素
{
if (*head == NULL) //没有元素的情况
{
*head = BuySlist(x);
}
else
{
Slist *cur = *head;
while (cur->next != NULL)
{
cur = cur->next;
}
cur->next = BuySlist(x);
}
}

void ListPopBack(Slist **head) //尾删元素
{
if (*head == NULL) //没有元素
{
return;
}
else if ((*head)->next == NULL) //只有一个元素
{
free(*head);
*head = NULL; //防止内存泄漏
}
Slist *cur = *head;
Slist *pos = cur;
while (cur->next != NULL)
{
pos = cur; //上下位置不能变
cur = cur->next;
}
free(cur);
cur = NULL;
pos->next = NULL; //此时pos为尾结点
}

void ListPushFront(Slist **head, DataType x) //头插元素
{
if (*head == NULL) //没有结点
{
*head = BuySlist(x);
return;
}
Slist *new;
new = BuySlist(x);
new->next = *head;
*head = new;
}

void ListPopFront(Slist **head)//头删元素
{
if (*head==NULL)
{
return;
}
//else if ((*head)->next == NULL)//一个节点 //注意这里不能写成*head->next，这是错的，存在优先级问题
//{
// free(*head);
// *head = NULL;
//}
Slist *cur = (*head)->next;
free(*head);
*head = cur;
}

void ListDestory(Slist **head) //销毁单链表
{
Slist *cur = *head;
while (cur)
{
Slist *next = cur->next;
free(cur);
cur = next;
}
*head = NULL;
}

Slist *Find(Slist *head, DataType x) //查找指定元素，返回下标
{
Slist *cur = head;
while (cur!=NULL)
{
if (cur->data == x)
{
return cur;

}
cur = cur->next;
}
return NULL;
}

void ListErase(Slist **head, Slist *pos) //删除任意节点
{
assert(pos&&*head);
if ((*head) == pos) //删除头节点
{
ListPopFront(head);
}
else if (pos->next == NULL) //删除尾节点
{
ListPopBack(head);
}
else
{
Slist *prev = *head;

while (prev->next != pos)
{
prev = prev->next;
}
prev = pos->next;
free(pos);
}
}

void Insert(Slist **head, Slist *pos, DataType x) //插入元素
{
assert(*head&&pos);
Slist *cur = *head;
Slist *tmp=NULL;
while (cur->next!=pos)
{

cur=cur->next;
}
/*tmp->data = x;
tmp->next = pos;*/
tmp = BuySlist(x);
tmp->next = pos;
cur->next = tmp;
}

void print(Slist *head) //打印元素
{
Slist *cur = head;
while (cur != NULL)
{
printf("%d->", cur->data);
cur = cur->next;
}
printf("NULL");
printf("\n");
}

void test1(Slist *list)
{
list = NULL;
ListPushback(&list, 1); //不能传list，实际上传的是地址的值，要传二级指针
ListPushback(&list, 7);
ListPushback(&list, 4);
ListPushback(&list, 15);
ListPushFront(&list, 10);
Slist *pos = Find(list, 7);
Insert(&list, pos, 2);
//ListPopFront(&list);
//ListPopBack(&list);
print(list);
}

int main()
{
test1(&List);
system("pause");
return 0;
}test函数根据自己的使用情况来调用任意函数