郝斌数据结构　　25 判断链表是否为空和求链表长度算法的演示

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

typedef struct Node
{
int data;               //数据域
struct Node *pNext;     //指针域
}NODE,*PNODE;   //NODE等价于struct Node     PNODE等价于struct Node *

PNODE creat_list(void);
void traverse_list(PNODE);
bool is_empty(PNODE pHead);
int length_list(PNODE pHead);
bool insert_list(PNODE pHead,int pos,int val);
bool delete_list(PNODE pHead,int pos,int *del_val);
void sort_list(PNODE pHead);

int main(void)
{
PNODE pHead = NULL;     //等价于struct Node * pHead = NULL;
int len;
pHead = creat_list();   //创建一个非循环链表,并将该链表的头结点的地址赋给pHead
traverse_list(pHead);

if(is_empty(pHead))
printf("链表为空\n");
else
printf("链表不为空\n");
len = length_list(pHead);
printf("链表的长度为:%d\n",len);
return 0;
}

PNODE creat_list(void)
{
int i;
int len; //用来存放有效节点的个数
int val; //用来临时存放用户输入的结点的值
printf("请输入你需要生成的链表的节点个数:len = ");
scanf("%d",&len);

PNODE pHead = (PNODE)malloc(sizeof(NODE));//分配了一个不存放数据的头结点
if(pHead == NULL)
{
printf("内存分配失败,程序终止\n");
exit(-1);
}

PNODE pTail = pHead;
pTail->pNext = NULL;

for(i=0; i<len; i++)
{
printf("请输入第%d个节点的值:",i+1);
scanf("%d",&val);

PNODE pNew = (PNODE)malloc(sizeof(NODE));
if(pNew == NULL)
{
printf("内存分配失败,程序终止\n");
exit(-1);
}
pNew->data = val;
pTail->pNext = pNew;
pNew->pNext = NULL;
pTail = pNew;
}
return pHead;
}

void traverse_list(PNODE pHead)
{
PNODE p = pHead->pNext;
while(p != NULL)
{
printf("%d    ",p->data);
p = p->pNext;
}
printf("\n");
}

bool is_empty(PNODE pHead)
{
if(pHead->pNext == NULL)
{
return true;
}
else
{
return false;
}
}

int length_list(PNODE pHead)
{
int len = 0;
PNODE p = pHead->pNext;
while(p != NULL)
{
len++;
p = p->pNext;
}
return len;
}