Question

我正在尝试创建一个动态列表，该列表应读取输入字符串并将每个字符串保存到lis的新节点中。该程序将打印每个节点，之后我想添加一个函数来删除节点，但是我遇到了很多错误，主要是因为我不太擅长使用指针并且我对数据结构不熟悉，有人可以帮我吗？

编辑：我更正了代码，现在我不再遇到错误了，但是程序似乎为每个节点打印一个字符，而不是为每个节点打印一个字符串，这是当前输出：

// Inserting and deleting nodes in a list
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// self-referential structure                       
struct listNode {                                      
   char *data; // each listNode contains a character 
   struct listNode *nextPtr; // pointer to next node
}; 
typedef struct listNode ListNode; // synonym for struct listNode
typedef ListNode *ListNodePtr; // synonym for ListNode*

// prototypes
void insert(ListNodePtr *sPtr, char *value);
int isEmpty(ListNodePtr sPtr);
void printList(ListNodePtr currentPtr);
void instructions(void);
int main(void)
{ 
   ListNodePtr startPtr = NULL; // initially there are no nodes
   char item; // char entered by user
   instructions(); // display the menu
   printf("%s", "? ");
   unsigned int choice; // user's choice
   scanf("%u", &choice);
   // loop while user does not choose 3
   while (choice != 3) { 
      switch (choice) { 
         case 1:
            printf("%s", "Enter a character: ");
            scanf("%c", &item);
            insert(&startPtr, &item); // insert item in list
            printList(startPtr);
            break;

         default:
            puts("Invalid choice.\n");
            instructions();
            break;
      } // end switch
      printf("%s", "? ");
      scanf("%u", &choice);
   } 
   puts("End of run.");
} 
// display program instructions to user
void instructions(void)
{ 
   puts("Enter your choice:\n"
      "   1 to insert an element into the list.\n"
      "   2 to delete an element from the list.\n"
      "   3 to end.");
}

// insert a new value into the list in sorted order
void insert(ListNodePtr *sPtr, char *value)
{ 
   ListNodePtr newPtr = malloc(sizeof(ListNode)); // create node

   if (newPtr != NULL) { // is space available
      newPtr->data= malloc(strlen(value)+1);
      strcpy(newPtr->data, value);
      newPtr->nextPtr = NULL; // node does not link to another node
      ListNodePtr previousPtr = NULL;
      ListNodePtr currentPtr = *sPtr;
      // loop to find the correct location in the list       
      while (currentPtr != NULL && value > currentPtr->data) {
         previousPtr = currentPtr; // walk to ...               
         currentPtr = currentPtr->nextPtr; // ... next node 
      }                                          
      // insert new node at beginning of list
      if (previousPtr == NULL) { 
         newPtr->nextPtr = *sPtr;
         *sPtr = newPtr;
      } 
      else { // insert new node between previousPtr and currentPtr
         previousPtr->nextPtr = newPtr;
         newPtr->nextPtr = currentPtr;
      } 
   } 
   else {
      printf("%s not inserted. No memory available.\n", value);
   } 
} 

int isEmpty(ListNodePtr sPtr)
{ 
   return sPtr == NULL;
}


// print the list
void printList(ListNodePtr currentPtr)
{ 
   // if list is empty
   if (isEmpty(currentPtr)) {
      puts("List is empty.\n");
   } 
   else { 
      puts("The list is:");
      // while not the end of the list
      while (currentPtr != NULL) { 
         printf("%s --> ", currentPtr->data);
         currentPtr = currentPtr->nextPtr;   
      } 
      puts("NULL\n");
   } 
}

以下是当前输出的示例：

    ./test
Enter your choice:
   1 to insert an element into the list.
   2 to delete an element from the list.
   3 to end.
? 1
Enter a character: The list is:

 --> NULL

? Test
Enter a character: The list is:

 --> T --> NULL

? Enter a character: The list is:

 --> T --> e --> NULL

? Enter a character: The list is:

 --> T --> e --> s --> NULL

? Enter a character: The list is:

 --> T --> e --> s --> t --> NULL

?

我想去的地方，例如：单词一->单词二等。

Answer 1

要获取用户输入，您正在使用

scanf("%c", &item);

这只会从他们的输入中得到一个字符。如果要获取字符串，可以将item更新为字符数组：

char item[20];

我还相信fgets更好地获取用户输入的字符串，如here所述。因此，使用以下代码可能会使您的程序更持久：

fgets(item, sizeof(item), stdin);

这些更改之后，输出如下：

Enter your choice:
1 to insert an element into the list.
2 to delete an element from the list.
3 to end.
? 1
Enter a character: The list is:

--> NULL

? Testing
Enter a character: The list is:

--> Testing
--> NULL

? What
Enter a character: The list is:

--> Testing
--> What
--> NULL

? About
Enter a character: The list is:

--> Testing
--> What
--> About
--> NULL

? This
Enter a character: The list is:

--> Testing
--> What
--> About
--> This
--> NULL

?

编辑：问题的代码中已经解决了以下问题。

newPtr->data是char，但是似乎您希望它是一个字符串。您应该更改结构定义，以使data改为char *。

如果您尝试打印字符串而不是单个字符，则应替换：

printf("%c not inserted. No memory available.\n", value);
// as well as
printf("%c --> ", currentPtr->data);

使用：

printf("%s not inserted. No memory available.\n", value);
// and
printf("%s --> ", currentPtr->data);

%c用于格式化单个字符，而%s用于打印字符串，并且必须与char *匹配

将字符串保存到动态列表中

1 个答案: