#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 *    //函数声明  pnode creat_list(); void traverse_list(pnode phead); 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,int*);  void sort_list(pnode phead);  int main() {     pnode phead = null;  //等价于struct node * phead = null；头结点      int val;          phead = creat_list();     traverse_list(phead);     if( is_empty(phead) )         printf("链表为空n");     else         printf("链表不空n");      int len = length_list(phead);     printf("链表长度是%dn",len);          if( insert_list(phead,4,33) )     {         printf("第四个节点插入数据成功!n");      }      else     {         printf("插入失败!n");     }     traverse_list(phead);          if( delete_list(phead,4,&val) )     {         printf("删除成功，您删除的元素是:%dn",val);      }      else     {         printf("删除失败！您删除的元素不存在!n");     }     traverse_list(phead);          sort_list(phead);     printf("链表由小到大排序n");     traverse_list(phead);          return 0; }   pnode creat_list() {     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节点的值          pnode phead = (pnode)malloc(sizeof(node));     if(null == phead)     {         printf("分配失败,程序终止");          exit(-1);     }      pnode ptail = phead;       ptail->pnext = null;          printf("请输入您需要生成的链表节点的个数:len = ");     scanf("%d",&len);          for(int 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(null == pnew)         {             printf("分配失败,程序终止");              exit(-1);         }          pnew->data = val;   //尾插法          ptail->pnext = pnew;         pnew->pnext = null;         ptail = pnew;  //ptail在不断的移动，相当于指向要插入节点上一个节点指针      }     return phead;  }  void traverse_list(pnode phead) {     pnode p = phead->pnext;     while(null != p)     {         printf("%d ",p->data);         p = p->pnext;     }     printf("n");     return; }   bool is_empty(pnode phead) {     if(null == phead->pnext)         return true;     else         return false; }  int length_list(pnode phead) {     pnode p = phead->pnext;     int len=0;      while(null != p)     {         ++len;         p = p->pnext;     }     return len; }  void sort_list(pnode phead)   //选择排序算法  {     pnode p,q;      int i,j,t;     int len = length_list(phead);          for(i=0,p=phead->pnext;i<len-1;++i,p=p->pnext)     {         for(j=0,q=p->pnext;j<len;++j,q=q->pnext)         {             if(p->data > q->data)   //类似于数组中的:a[i]>a[j]              {                 t = p->data;//类似于数组中的:t = a[i];                 p->data = q->data;//类似于数组中的:a[i] = a[j];                 q->data = t;//类似于数组中的:a[j] = t;             }          }     }     return; }  bool insert_list(pnode phead,int pos,int val) {     int i=0;     pnode p = phead;          while(null!=p && i<pos-1)     {         p = p->pnext;         ++i;     }     if(i>pos-1 || null==p)         return false;              pnode pnew =(pnode)malloc(sizeof(node));     if(null == pnew)     {         printf("动态分配内存是啊比!n");         exit(-1);     }     pnew->data = val;     pnode q = p->pnext;     p->pnext = pnew;     pnew->pnext = q;     return true; }  bool delete_list(pnode phead,int pos,int* pval) {     int i=0;     pnode p = phead;          while(null!=p->pnext && i<pos-1)     {         p = p->pnext;         ++i;     }     if(i>pos-1 || null==p->pnext)         return false;              pnode q = p->pnext;   //将要删除的节点赋值给临时指针q      *pval = q->data;          //删除p节点后面的节点     p->pnext = p->pnext->pnext;     free(q);     q = null;      return true;     }