为什么我的链表在遍历时会跳过第一个节点？

Question

我正在学习 C，目前正在学习动态内存分配和链表，我运行遇到了一个问题。我找到了这个并遵循了答案。但是我的程序在打印时仍然跳过我的第一个节点。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct record
{
  int id;
  char name[257];
  float age;
  struct record *next;
};

int main(void)
{

  int i = 1;
  struct record *firstrecord = (struct record *)malloc(sizeof(struct record));
  firstrecord->id = 1000;
  char firstname[] = "John Doe";
  memcpy(firstrecord->name, firstname,strlen(firstname) + 1);
  firstrecord->age = 24.5;
  firstrecord->next = NULL;

  struct record *mostrecentlycreated = firstrecord;

  int iyes = 1;
  char cyes;
  int yes = 1;
  while (yes == iyes)
  {
    
      // build next node
      mostrecentlycreated->next = (struct record *)malloc(sizeof(struct record));
      // change data in new record
      int newid;
      char newname[257];
      char temp;
      float newage;
      char cnewage[257];
    
      printf("Enter the name: ");
      fgets(newname,257,stdin);
    
      newid = 1000 + i;

      printf("Enter the person's age: ");
      fgets(cnewage,257,stdin);
      newage = atof(cnewage);
    
      mostrecentlycreated->id = newid;
      memcpy(mostrecentlycreated->name,newname,strlen(newname) + 1);
      mostrecentlycreated->age = newage;
      mostrecentlycreated = mostrecentlycreated->next;
      mostrecentlycreated->next = NULL;


      i++;
      // decide whether or not to keep going
      printf("Do you wish to continue? 1\0 ");
      
      fgets(&cyes,1,stdin);
      iyes = atoi(&cyes);
    
    
      scanf("%c",&temp);
    
  }
  struct record *traverse = firstrecord;
  while (traverse != NULL)
  {
    printf("Employee id is %i; Employee Name is %s; Employee Age is %f\n",traverse->id,traverse->name,traverse->age);
    traverse = traverse->next;
  }

  free(firstrecord);
  free(mostrecentlycreated);
  return 0;
}

这是我的输出：

Enter the name: john doe
Enter the person's age: 23
Do you wish to continue? 1[=11=] 0
Employee id is 1001; Employee Name is john doe
; Employee Age is 23.000000
Employee id is 0; Employee Name is ; Employee Age is 0.000000

为什么打印不出第一人称？

Answer 1

创建第一个节点后，循环会在每次迭代时创建一个新节点，但它将用户的输入分配给列表中的 previous 节点，而不是当前节点正在添加到列表中。因此，在第一次迭代中，您将覆盖第一个节点的数据，然后附加第二个空节点。然后在第 2 次迭代中，您将覆盖第 2 个节点的数据，并附加一个空白的第 3 个节点。等等。

试试这个：

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

struct record
{
  int id;
  char name[257];
  float age;
  struct record *next;
};

int main(void)
{
  int i = 1;

  struct record *firstrecord = (struct record *)malloc(sizeof(struct record));
  firstrecord->id = 1000;
  strncpy(firstrecord->name, "John Doe", 257);
  firstrecord->age = 24.5;
  firstrecord->next = NULL;

  struct record *mostrecentlycreated = firstrecord;

  const int cyes = 1;
  int iyes = 1;

  while (iyes == cyes)
  {    
      // build next node
      struct record *newrecord = (struct record *)malloc(sizeof(struct record));

      // change data in new record    
      newrecord->id = 1000 + i;

      printf("Enter the name: ");
      fgets(newrecord->name, 257, stdin);
    
      printf("Enter the person's age: ");
      scanf("%f", &(newrecord->age));
    
      newrecord->next = NULL;

      mostrecentlycreated = newrecord;

      ++i;

      // decide whether or not to keep going
      printf("Do you wish to continue? 1\0 ");
      scanf("%d", &iyes);
  }

  struct record *traverse = firstrecord;
  while (traverse != NULL)
  {
    printf("Employee id is %i; Employee Name is %s; Employee Age is %f\n", traverse->id, traverse->name, traverse->age);
    traverse = traverse->next;
  }

  traverse = firstrecord;
  while (traverse != NULL)
  {
    struct record *nextrecord = traverse->next;
    free(traverse);
    traverse = nextrecord;
  }

  return 0;
}

为什么我的链表在遍历时会跳过第一个节点？

Why is my linked list when being traversed skipping the first node?

c

pointers

linked-list