二重リンクリストの先頭と末尾に挿入 - 最後のテールアイテムのみを出力します

Question

試験のために勉強するために二重リンクリストを実装しようとしています。 - リストの先頭に挿入するだけで、正しく印刷されます。しかし、リストの末尾に挿入すると、最後のテールアイテムだけが出力されます。以下は私のフルコードです：

/* 
    - Q2: Write a function that takes a LinkedList struct pointer and inserts at the head of the linked list. 

    - Q3. Write a function that takes a LinkedList struct pointer and frees all memory associated with it. (
      For a solution, see fancy-linked-lists.c, attached above.) 

    - Q4 Review all the functions from today's code and give their big-oh runtimes. 

    - Q5: Implement functions for doubly linked lists: 
     - tail_insert(), 
     - head_insert(), 
     - tail_delete(), 
     - head_delete(), 
     - delete_Nth(). 
     - Repeat these exercises with doubly linked lists in which you maintain a tail pointer. 
     - How does the tail pointer affect the runtimes of these functions? 
     - Are any of these functions more efficient for doubly linked lists with tail pointers than they are for singly linked lists with tail pointers? 
*/ 

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

typedef struct node 
{ 
    int data; 
    struct node *next; 
    struct node *prev; 
} node; 

node *createNode(int data) 
{ 
    node *ptr = NULL; 
    ptr = malloc(sizeof(node)); 
    if(ptr == NULL) 
    { 
     printf("space could not be allocated\n"); 
     return NULL; 
    } 

    ptr->data = data; 
    ptr->next = NULL; 
    ptr->prev = NULL; 

    return ptr; 
} 

node *tailInsert(node *head, int data) 
{ 
     if(head->next == NULL) 
    { 
     node *temp; 
     temp = createNode(data); 
     temp->next = NULL; 
     temp->prev = head; 
     head->next = temp; 
     return head; 
    } 
    tailInsert(head->next, data); 
} 

node *frontInsert(node *head, int data) 
{ 
    node *newHead; 

    if(head == NULL) 
    { 
     return createNode(data); 
    } 

    newHead = createNode(data); 
    newHead->next = head; 
    newHead->prev = NULL; 

    return newHead; 
} 

node *destroy_linked_list(node *list) 
{ 
    /*if (list == NULL) 
     return NULL; 

    // Free the entire list within this struct. 
    destroy_list(list->head); 

    // Free the struct itself. 
    free(list); 

    return NULL; 
    */ 
} 

void printList(node *head) 
{ 
    if (head == NULL) 
    { 
     printf("Empty List\n"); 
     return; 
    } 

    for(; head != NULL; head = head->next) 
     printf("%d ", head->data); 

    printf("\n"); 
} 

int main(void) 
{ 
    node *head = NULL; 

    head = frontInsert(head, 1); 
    head = frontInsert(head, 2); 
    head = frontInsert(head, 3); 
    head = tailInsert(head, 4); 
    head = tailInsert(head, 5); 
    head = tailInsert(head, 6); 

    printList(head); 

    system("PAUSE"); 
    return 0; 
} 

私は助けてくれてありがとう！

Answer 1

tailInsertからtemp（最終ノード）を返し、headに割り当てます。末尾に挿入する場合は、ヘッドポインタを変更しないでください。メインで

void tailInsert(node *head, int data) 
{ 
    if(head->next == NULL) 
    { 
     node *temp; 
     temp = createNode(data); 
     temp->next = NULL; 
     temp->prev = head; 
     head->next = temp; 
     return ; 
    } 
    tailInsert(head->next, data); 
} 

、あなたが