学习笔记——C语言实现单链表的基本操作：创建、输出、插入结点、删除结点、逆序链表

链表是最简单的一种数据结构，是每个软件开发者必须掌握的，也是企业招聘时最常考的内容，因此，在这里总结一下单链表的一些基本操作。

注：这里是单向无环链表，头结点中存放了数据，换句话说就是头结点和其他结点没什么区别，你也可以说成不带头结点的链表。下面就是链表操作的源代码：

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

typedef struct Node
{
int data;
struct Node *next;
}Lnode;

void printList(Lnode *head);
Lnode *createList();
Lnode *insertList(Lnode *head,int elem,int position);
Lnode *deleteElem(Lnode *head,int elem);
Lnode *reverseList(Lnode *head);

int main()
{
Lnode *head;
int elem,position;

head = createList();
printList(head);

printf("Input the element and the position:/n");
scanf("%d %d", &elem, &position);
head = insertList(head,elem,position);
printList(head);

head = reverseList(head);
printf("After reversed:/n");
printList(head);

printf("Input the element you want to delete:/n");
scanf("%d",&elem);
head = deleteElem(head, elem);
printList(head);

return 0;
}

/*传入表头指针，打印链表*/
void printList(Lnode *head)
{
Lnode *p = head;

if (p == NULL)
{
printf("List is empty!/n");
return;
}
while (p != NULL)
{
printf("%d ", p->data);
p = p->next;
}
printf("/n");
}

/*创建一个新链表，返回表头指针*/
Lnode *createList()
{
Lnode *head, *current, *p;
int data;

head = (Lnode *)malloc(sizeof(Lnode));
p = head;

printf("Input integers,0 to break:/n");
scanf("%d",&data);

if (data != -1)
{
p->data = data;
}
else
{
head->next = NULL; //只有头结点的情况
return head;
}

while (1)
{
scanf("%d", &data);
if (data == -1)
{
break;
}

current = (Lnode *)malloc(sizeof(Lnode));
current->data = data;
p->next = current;
p = p->next;
}
p->next = NULL;

return head;
}

/*链表的插入操作，head为链表表头，elem为要插入的元素，position为插入的位置
*将elem插入至第position个结点后，position<=0时，插入至头结点后
*/
Lnode *insertList(Lnode *head,int elem,int position)
{
Lnode *current, *p;
int i = position - 1;
current = head;

/*找到第position个节点*/
while (i > 0 && current->next != NULL)
{
current = current->next;
i--;
}

if (i > 0) //结点数小于输入的位置position
{
printf("Position is wrong!/n");
return head;
}

p = (Lnode *)malloc(sizeof(Lnode));
p->data = elem;
p->next = current->next;
current->next = p;

return head;
}

/*删除链表head中所有的元素elem，返回头结点head*/
Lnode *deleteElem(Lnode *head,int elem)
{
Lnode *p = head;
Lnode *ptemp;
int flag = 0; //记录便表中elem的个数

while (1)
{
if (head->data == elem) //删除头结点的情况
{
flag++;
head = head->next;
free(p);
p = head;
}
else
{
break;
}
}

while (p->next != NULL)
{
if (p->next->data == elem )
{
flag++;
ptemp = p->next;
if (p->next->next != NULL)
{
p->next = p->next->next;
free(ptemp);
ptemp = NULL;
}
else //最后一个结点
{
free(ptemp);
ptemp =NULL;
p->next = NULL;
break;
}
}
else //没有删除结点时，查询下一个结点
{
p = p->next;
}
}
printf("%d number '%d' was found and deleted./n", flag, elem);
return head;
}

/*将链表逆序，该链表不带头结点。*/
Lnode *reverseList(Lnode *head)
{
Lnode *current, *pnext, *ptemp;

current = head;
pnext = head->next;
head->next =NULL;

while (pnext != NULL)
{
ptemp = pnext->next;
pnext->next = current;
current = pnext;
pnext = ptemp;
}

head = current;
return head;
}