c - "search"c中的链表

Question

我为我的链接列表菜单添加了一个“搜索”功能，但我不知道我的代码有什么问题。当我输入一个名称不在列表中的搜索键时，程序不会打印“搜索键:%s 未找到!”，而是会停止。如何解决？关于如何改进我的程序有什么建议吗？

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

 struct list
    {
char name[20];
int age;
char gender[10];
     struct list *next;
     };

   void main(void)
   {
      struct list *HEAD = NULL;
         struct list *temp,*current, *trav;
        struct list *prev,*temp1,*temp2;

       char choice;


while(1)
{
    clrscr();
    printf("MENU\n");
    printf("A) ADD\n");
    printf("B) DISPLAY\n");
    printf("C) DELETE\n");
    printf("D) SEARCH\n");
    printf("X) EXIT\n");

    scanf("%c", &choice);
    switch(toupper(choice))
{
 case 'A':
            temp= (struct list*)malloc(sizeof(struct list));
            temp->next=NULL;
            printf("Fill-Up the following:\n");
            printf("Name:");
            fflush(stdin);
            gets(temp->name);
            printf("Age:");
            fflush(stdin);
            scanf("%d",&temp->age);
            printf("Gender:");
            fflush(stdin);
            gets(temp->gender);


            if(HEAD == NULL)
            {
                      HEAD = temp;

            }
            else if(HEAD!=NULL)
            {
              for(trav=HEAD; trav->next != NULL; trav= trav->next);
              trav->next=temp;
            }
            else
            {
            printf("Not Enough Memory!\n");
            }

 break;
 case 'B':

          if(HEAD==NULL)
          {
          printf("Linked List is Empty!\n");
          getch();
          }
          else{
          for(trav=HEAD; trav != NULL; trav=trav->next )
          {

                printf("\nName: %s\n", trav->name);
                printf("Age: %d\n", trav->age);
                printf("Gender: %s\n\n", trav->gender);
                     }
                     getch();

          }

 break;

case 'C' :
    temp1=( struct list*)malloc(sizeof(struct list));
    temp1->next=NULL;
    if(HEAD==NULL)
    {
    printf("No item to be delete. List is Empty!\n");
    getch();
        }
    else {
        printf("Enter The Name of the item you want to Delete: ");
        fflush(stdin);
        gets(temp1->name);
        current=HEAD;

        if(strcmp(temp1->name,current->name)== 0)
        {
            HEAD=HEAD->next;
            free(current);
            printf("Item has been successfully deleted from the list.\n");
            getch();
            }
        else
         {
            for(prev=HEAD,trav=HEAD->next; strcmp(trav->name,temp1->name) == 1 ; trav=trav->next,prev=prev->next);

                  if(trav==NULL)
                  {
                  printf("Name: %s not found!", temp1->name);
                  getch();
                  }
                  else{
                prev->next=trav->next;
                free(trav);
                printf("Item has been successfully deleted from the list.\n");
                getch();
                }

            }
        }

    break;
 case 'D':
        temp2=( struct list*)malloc(sizeof(struct list));
    temp2->next=NULL;
        if(HEAD==NULL)
        {
         printf("No item to search. List is Empty.\n");
         getch();
        }
        else{
                printf("Enter Name (Search Key): ");
                fflush(stdin);
                gets(temp2->name);

                int count=0;

                       struct list *trav2=HEAD;
                    while( trav2 !=NULL)
                     {
                       for(struct list *trav1=trav2; strcmp(trav1->name,temp2->name)!=0;trav1=trav1->next);
                           if(trav1!=NULL)
                            {
                    printf("\nName: %s\n", trav1->name);
                    printf("Age: %d\n", trav1->age);
                    printf("Gender: %s\n",trav1->gender);
                    trav2=trav1->next;
                    count++;
                             }
                    else {
                        trav2=NULL;
                        }
                    }
                    getch();
                        if(count==0)
                        {   
                            printf("Search Key: %s Not Found!\n", temp2->name);
                                getch();
                                    }
        }   

 break;
 case 'X':
 if(HEAD!=NULL){free(HEAD); }
if(trav!=NULL){ free(trav); } 
    if(trav1!=NULL){ free(trav1); } 
     if(trav2!=NULL){ free(trav2); } 
   if(temp!=NULL){ free(temp); } 
   if(temp1!=NULL){ free(temp1); } 
 exit(1);

 break;

}

}
}

Answer 1

在你的搜索程序中..

for(struct list *trav1=trav2; strcmp(trav1->name,temp2->name)!=0;trav1=trav1->next);

此处 trav1 在列表末尾将为空，但您仍在继续并取消引用它。像这样在你的 for 循环中添加一个检查 temp1:

 for(struct list *trav1=trav2; trav1 && (strcmp(trav1->name,temp2->name)!=0);trav1=trav1->next);

或者，为了更好的可读性:

 for (struct list *trav1 = trav2; trav1 != NULL; trav1 = trav1->next)
 {
     if (strcmp(trav1->name, temp2->name) !=0 )
         break;
 }

关于您的代码的一些其他评论:

1. 不要使用 fflush(stdin) 使用类似这样的东西，因为标准不能保证它能正常工作。

   int c;
   while ((c = getchar()) != EOF && c != '\n')
       ;
   

2. 停止使用 gets()。安全地使用 gets() 是不可能的。请改用 fgets()(但请注意，它会在 gets() 丢弃它的地方保留换行符)。