如何在列表中插入特定数量的元素？

Question

我试图通过使用 size_t n 在列表中插入特定数量的元素（来自结构的四个元素，每个元素代表一个数据包）但是当我运行主程序时它什么都不显示。我如何在插入函数中定义大小，以便当更多数据包（四组）尝试插入列表时，它们将因为列表的大小而无法插入？

    struct Packet
    {
     int rollnumber;
     int src;
     int dest;
     double gentime;
     struct Packet *next;
    }* head;

  void insert(int rollnumber, int src, int dest, double gentime, size_t n)
   {
     if (n==0) n=(size_t)-1;
     struct Packet * packet = (struct Packet *) malloc(sizeof(struct Packet));
     for ( struct Packet * temp = head; n-- && temp != NULL; temp = temp->next ){
       packet->rollnumber = rollnumber;
       packet->src=src;
       packet->dest=dest;
       packet->gentime = gentime;
       packet->next = NULL;

       if(head==NULL){
          head = packet;
       }
       else{
          packet->next = head;
          head = packet;
       }
    }

    }

     
    void display()
    {
     struct Packet * temp = head;
     while(temp != NULL)
     {
       printf("Roll Number: %d\n",temp->rollnumber);
       printf("src: %d\n", temp->src);
       printf("dest: %d\n", temp->dest);
       printf("gentime: %0.1f\n\n", temp->gentime);
       temp = temp->next;
      }
   }

Answer 1

编辑： 下面的新代码是一个完整的工作示例。它应该给你足够的开始去休息。

您创建了上面的数据包，但从未真正将其放入您的链中。这将创建它并尝试找到插入它的正确位置：

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

struct Packet
{
   int rollnumber;
   int src;
   int dest;
   double gentime;
   struct Packet *next;
}* head;

void insert(int rollnumber, int src, int dest, double gentime, size_t n)
{
    /* Assuming you're trying to insert these values at point n */

    if (n >= 15) {
        printf("no %d!\n", n);
        return;
    }

    /* create the packet to insert */
    struct Packet * packet = (struct Packet *) malloc(sizeof(struct Packet));
    packet->rollnumber = rollnumber;
    packet->src=src;
    packet->dest=dest;
    packet->gentime = gentime;
    packet->next = NULL;

    /* now find the point where it should be inserted */
    if (n == 0 || head == NULL) {
        /* it should be first! */
        packet->next = head;
        head = packet;
    } else {
        struct Packet *temp = head;
        for ( ; n > 1 && temp != NULL && temp->next != NULL ; temp = temp->next, n-- ){
        }
        if (temp != NULL) {
            /* put ourselves in the middle (or the end if packet->next is NULL) */
            packet->next = temp->next;
            temp->next = packet;
        }
    }
}

void display()
{
    printf("-----------------\n");
    struct Packet * temp = head;
    while(temp != NULL)
        {
            printf("Roll Number: %d\n",temp->rollnumber);
            printf("src: %d\n", temp->src);
            printf("dest: %d\n", temp->dest);
            printf("gentime: %0.1f\n\n", temp->gentime);
            temp = temp->next;
        }
}

int main() {
    insert(1,1,1,1,10); /* legal, will just append */
    display();

    insert(2,2,2,2,0); /* insert before 1 */
    display();

    insert(3,3,3,3,2); /* insert after 2 */
    display();

    insert(4,4,4,4,1); /* after 2, and before 3 */
    display();

    insert(5,5,5,5,15); /* illegal */
}

如何在列表中插入特定数量的元素？

How can I insert a specific number of elements in a list?

c

list

singly-linked-list