顯示、打印和在正確位置刪除的問題（鏈表）

Question

在嘗試在鏈接列表中添加和打印時，代碼在中間stops 。 並且當它運行時（在刪除某些函數之后），刪除和中間的 si 不在定義的位置。

#include <stdio.h>
#include <stdlib.h>
struct FlavorList{
    char name[100];
    struct FlavorList* next ; 
};
void addAtfront(struct FlavorList **head){
    struct FlavorList *new_cake = (struct FlavorList*)malloc(sizeof(struct FlavorList));
    printf("First cake: ");
    scanf("%s",new_cake->name);
    new_cake->next = *head ; 
    *head = new_cake ; 
}
void addAtback(struct FlavorList **head){
    struct FlavorList* new_cake = (struct FlavorList*) malloc(sizeof(struct FlavorList)); 
    printf("Second cake : ");
    scanf("%s",new_cake->name);
    new_cake->next = NULL;
    struct FlavorList *last = *head;  
    if (*head == NULL)    {
       *head = new_cake;
       return;    
} 
    while (last->next != NULL)
        last = last->next;
    last->next = new_cake;
    return;   
}
void addInbetween(struct FlavorList  ** head , int pos){
    struct FlavorList * new_cake = (struct FlavorList *) malloc(sizeof(struct FlavorList ));
    printf("Between cake : ");
    scanf("%s",new_cake->name);
    new_cake->next = NULL;
    struct FlavorList  *zig = *head ; 
    int count = 0 ; 
    while(zig!=NULL && count<=pos){
        count ++ ; 
        zig=zig->next ; 
    }
    new_cake->next = zig->next ; 
    zig->next = new_cake ; 
}
void delete(struct FlavorList **head, int pos){
    struct FlavorList*current=*head;
    struct FlavorList*previous=*head;
    if(head ==NULL)    {
        printf("List is empty");
    }
    else if (pos==1)    {
        *head=current->next;
        free(current);
        current=NULL;
    }
    else    {
        while(pos!=1)        {
            previous=current;
            current=current->next;
            pos--;
        }
        previous->next=NULL;
        free(current);
        current=NULL;
    }
}
void display(struct FlavorList  **head){
    struct FlavorList  *zig = * head ;
    while(zig != NULL){
        printf("List of cakes");
        printf("%s",zig->name);
        printf(" ");
        zig=zig->next; 
    }
    printf("\n");
}
int main(){
    struct FlavorList *head = NULL ; 
    printf("--------------------------------\n");
    printf("-----------Cake Shop------------\n");
    printf("--------------------------------\n");
    addAtfront(&head);
    addAtback(&head);
    addInbetween(&head,2);
    display(&head);
    printf("Deleting cake at position 1: \n");
    delete(&head,1);
    printf("Present of now:\n");
    display(&head);
}

我得到的輸出。

--------------------------------
-----------Cake Shop------------
--------------------------------
First cake: First
Second cake : Second
Between cake : Between


...Program finished with exit code 0
Press ENTER to exit console.

當我再添加一個 addatfront 和 addatback 時，我可以進入顯示和刪除部分，但它們不在定義的位置。 之后的輸出：

--------------------------------
-----------Cake Shop------------
--------------------------------
First cake: First1
First cake: First2
Second cake : Second1
Second cake : Second2
Between cake : Middle
List of cakes
First2
First1
Second1
Second2
Middle

Deleting cake at position 1: 
Present of now:
List of cakes
First1
Second1
Second2
Middle

Answer 1

所以這是我處理您的代碼的方式。 我將完成並解釋這個答案，但只是為了讓你有一些東西可以看，我會給出整個代碼

MAX_NAME_SIZE

此宏將允許您快速更改名稱參數的最大允許大小。

鏈接列表的更改：

讓我們從我更改結構的方式開始，我已將其轉換為 typedef，因此分配會更容易（這樣我們不必每次都鍵入 struct）並且我允許給定任何大小名稱參數。

哨兵

現在更重要的更改將允許您進一步簡化代碼。 這是一個 wiki 頁面來了解它是什么Sentinel ，但簡單地說，它用作頭節點，它包含一個我們不想讀取的值，因此允許將頭作為簡單指針而不是雙精度指針傳遞指針！

錯誤.h

我添加了此標頭以允許以更簡潔的方式管理錯誤異常，例如當您要刪除節點的索引超出范圍時。

釋放鏈表

我已經實現了一個簡單的 free 函數，一旦你完成了所有需要的操作，它將釋放你的鏈表，否則我們將面臨內存泄漏！

    #include <stdio.h>
    #include <stdlib.h>
    #include <err.h>
    
    #define MAX_NAME_SIZE 100
    
    typedef struct FlavorList
    {
        char *name;
        struct FlavorList *next;
    }FlavorList;
    
    FlavorList * FlavorListBuildSentinel()
    {
        FlavorList *cake_sentinel = malloc(sizeof(FlavorList));
        cake_sentinel->name = malloc(sizeof(char));
        cake_sentinel->next = NULL;
        return cake_sentinel;
    }
    
    void addAtfront(FlavorList *head)
    {
        printf("Adding a new cake in the front!\n");
        char * new_name = malloc(sizeof(char)*(MAX_NAME_SIZE+1));
        scanf("%s",new_name);
        FlavorList *new_cake = malloc(sizeof(FlavorList));
        new_cake->name = new_name;
        new_cake->next = head->next;
        head->next = new_cake;
    }
    
    
    void addAtback(FlavorList *head)
    {
        printf("Adding a new cake in the back!\n");
        FlavorList *new_cake = malloc(sizeof(FlavorList));
        while(head->next!=NULL)
        {
            head = head->next;
        }
        char * new_name = malloc(sizeof(char)*(MAX_NAME_SIZE+1));
        scanf("%s",new_name);
        new_cake->name = new_name;
        new_cake->next = head->next;
        head->next = new_cake;
    }
    
    void addInbetween(FlavorList *head,int pos)
    {
        printf("Adding a new cake at pos: %d!\n",pos);
        while(pos && head->next!=NULL)
        {
            head = head->next;
            pos--;
        }
        //If the pos is still not 0 and the list is out of range, we quit!
        if(pos!=0)
        {
            errx(1, "Index out of range!");
        }
        //If not do the insertion
        FlavorList *new_cake = malloc(sizeof(FlavorList));
        char * new_name = malloc(sizeof(char)*(MAX_NAME_SIZE+1));
        scanf("%s",new_name);
        new_cake->name = new_name;
        new_cake->next = head->next;
        head->next = new_cake;
    }
    
    void delete(FlavorList *head, int pos)
    {
        while(pos && head->next!=NULL)
        {
            head = head->next;
            pos--;
        }
        //If the pos is still not 0 and the list is out of range, we quit!
        if(pos!=0 || head->next == NULL)
        {
            errx(1, "Index out of range!");
        }
        FlavorList * tmp = head->next;
        if(head->next->next!=NULL)
        {
            head->next = head->next->next;
        }
        else
        {
            head->next = NULL;
        }
        free(tmp->name);
        free(tmp);
    }
    
    
    void display(FlavorList* head)
    {
       printf("List of cake names\n");
       int cpt = 1;
       while(head->next)
       {
           head = head->next;
           printf("Cake name at position: %d is %s\n",cpt,(head->name));
           cpt++;
       }
       printf("\n");
    }
    
    //Frees the allocated node
    void FlavorListFree(FlavorList* head)
    {
        FlavorList* previous;
        while (head)
        {
            previous = head;
            head = head->next;
            free(previous->name);
            free(previous);
        }
    }
    
    
    int main()
    {
        FlavorList * head = FlavorListBuildSentinel();
    
        printf("--------------------------------\n");
        printf("-----------Cake Shop------------\n");
        printf("--------------------------------\n");
        addAtfront(head);
        addAtback(head);
        addInbetween(head,2);
        display(head);
        printf("Deleting cake at position 1: \n");
        delete(head,1);
        printf("Present of now:\n");
        display(head);
        FlavorListFree(head);
    }

我已經測試了所有功能以及邊緣情況和異常，它們工作得很好，請不要猶豫，提出任何問題！ 此致，