总结了一些指针易出错的常见问题（五）

指针与链表及其操作

//结构体定义
typedef  struct _person{
    char* firstname;
    char* lastname;
    char* title;
    unsigned int age;
}Person;
Person person;
//分配内存
Person *ptrPerson;
ptrPerson = (Person*) malloc (sizeof(Person));

　　为结构体分配内存

#include<stdio.h>

int main()
{
    typedef struct _alternatePerson{
        char* firstname;
        char* lastname;
        char* title;
        short age;
    }AlternatePerson;;

     //AlternatePerson otherperson;
     AlternatePerson people[30];
    typedef struct _Person{
        char* firstname;
        char* lastname;
        char* title;
        unsigned int age;
    }Person; 
    Person person;
    
    printf("%d\n",sizeof(Person));
    printf("%d\n",sizeof(people));
    return 0;
    
}

　　指针支持数据结构

链表

队列

栈

树（二叉树）

　　

队列是一种现行数据结构，行为类似排队，（入队和出队）

/*写一函数建立一个有3名学生数据的单向动态链表*/
 #include<stdio.h>
 #include<malloc.h>
 //#define NULL 0
 #define LEN sizeof(struct student)
 
 struct student
 {
     long num;
     float score;
     struct student *next;
  };
  int n;
  struct student *creat(void)
  {
      struct student *head;
      struct student *p1,*p2;
      n=0;
      p1=p2=(struct student*)malloc(LEN);
      scanf("%ld,%f",&p1->num,&p1->score);
      head=NULL;
      while(p1->num!=0)
      {
          n=n+1;
          if(n==1) head=p1;
          else
          p2->next=p1;
          p2=p1;
          p1=(struct student*)malloc(LEN);
          scanf("%ld,%f",&p1->num,&p1->score);
       } 
       p2->next=NULL;
       return(head);
  }
  
  void print(struct student *head)
  {
      struct student *p;
      printf("\n Now,These %d record are:\n",n);
      p=head;
      if(head!=NULL)
          do
          {
              printf("%ld %5.1f\n",p->num,p->score);
              p=p->next;
          }while(p!=NULL);
  }
  
  struct student *del(struct student *head,long num)
  {
      struct student *p1,*p2;
      if(head==NULL) {printf("\nlist is NULL.\n"); return head; }
      p1=head;
      while(num!=p1->num&&p1->next!=NULL)
      {
          p2=p1;p1=p1->next;
    }
    if(num==p1->num)
    {
        if(p1==head) head=p1->next;
        else p2->next=p1->next;
        printf("delete:%ld\n",num);
        n=n-1;
    }
    else printf("%ld not have been found: \n",num);
    return (head);
  }
 
 /* insert */
 struct student *insert(struct student *head,struct student *stud)
 {
     struct student *p0,*p1,*p2;
     p1=head;
     p0=stud;
     if(head==NULL) { head=p0;p0->next=NULL;}
     else 
         {
             while((p0->num>p1->num)&&(p1->next!=NULL))
             {
                 p2=p1;
                 p1=p1->next;
             }
             if(p0->num<=p1->num){
                 if(head==p1) head=p0;
                 else p2->next=p0;
                 p0->next=p1;
             }
             else
             {
                 p1->next=p0;p0->next=NULL;
             }     
         }
          n=n+1;
          return(head);
 }
 int main()
 {
      struct student *head,stu;
      long del_num;
      printf("input records: \n");
      head=creat();
      print(head);
      printf("\n input the deleted number:");
      scanf("%ld",&del_num);
      head=del(head,del_num);
      print(head);
      printf("\n input the inserted record:");
      scanf("%ld,%f",&stu.num,&stu.score);
      head=insert(head,&stu);
      print(head);
 }