鏈表，遞歸

Question

我正在研究一個程序，使用遞歸打印出反向鏈表。我的遞歸代碼似乎只打印出最後一部電影，然後停止。 「獲取」在Microsoft Visual Studio中不起作用，所以我正在使用compile online的c ide並且無法訪問調試器。預期產出低於。該代碼也在下面發佈。

Enter first movie title: 
Titanic 

Enter your rating<0-10>: 
5 

Enter next movie title: 
Inception 

Enter your rating<0-10>: 
8 

Here is the movie list:                                   
Movie: Titanic Rating: 8                                  
Movie: Inception Rating: 9                                  
Display list from tail to head:                                 
Here is the movie list:                                   
Movie: Inception Rating : 9 
Movie: Titanic Rating : 8 

實際輸出：

Here is the movie list:                                   
Movie: Titanic Rating: 8                                  
Movie: Inception Rating: 9                                  
Display list from tail to head:                                 
Here is the movie list:                                   
Movie: Inception Rating : 9 

#include <stdio.h> 
#include <stdlib.h>  /* has the malloc prototype  */ 
#include <string.h>  /* has the strcpy prototype  */ 
#define TSIZE 45  /* size of array to hold title */ 

struct film 
{ 
    char title[TSIZE]; 
    int rating; 
    struct film* next; /* points to next struct in list */ 
    struct film* prev; 
}; 

int main(void) 
{ 
    struct film *head = NULL, *prev, *current, *temp; 
    struct film *tail = NULL; 
    char input[TSIZE]; 

    /* Gather and store information   */ 
    puts("Enter first movie title:"); 
    while (gets(input) != NULL && input[0] != '\0') 
    { 
     current = (struct film *) malloc(sizeof(struct film)); //request a new film struct 
     if (head == NULL)  /* first structure  */ 
      head = current; 
     else     /* subsequent structures */ 
      prev->next = current; 
     current->next = NULL; 
     strcpy(current->title, input); 
     puts("Enter your rating <0-10>:"); 
     scanf("%d", &current->rating); 
     while (getchar() != '\n') 
      continue; 
     puts("Enter next movie title (empty line to stop):"); 
     prev = current; 
     tail = current; 
    } 
    /* Show list of movies     */ 
    if (head == NULL) 
     printf("No data entered. "); 
    else 
     printf("Here is the movie list:\n"); 
    current = head; 
    while (current != NULL) 
    { 
     printf("Movie: %s Rating: %d\n", 
      current->title, current->rating); 
     current = current->next; 
    } 

    puts("Display list from tail to head:"); 
    if (tail == NULL) 
     puts("No data entered."); 
    else 
     puts("Here is the movie list: "); 
    current = tail; 
    while (current != NULL) 
    { 
     printf("Movie: %s Rating : %d\n", current->title, current->rating); 
     current = current->prev; 
    } 

    /* Program done, so free allocated memory */ 
    current = head; 
    while (current != NULL) 
    { 
     temp = current->next; 
     free(current); 
     current = temp; 
    } 

    return 0; 
} 

Answer 1

你不填充電流 - >分組字段結構在這裏：

if (head == NULL)  /* first structure  */ 
    { 
     head = current; 
     current->prev = NULL; 
    } 
    else     /* subsequent structures */ 
    { 
     current->prev = prev; 
     prev->next = current; 
    } 

Answer 2

您未設置插入節點的數據成員prev。你應該寫例如

if (head == NULL)  /* first structure  */ 
    { 
     head = current; 
     current->prev = NULL; 
    } 
    else     /* subsequent structures */ 
    { 
     prev->next = current; 
     current->prev = tail; 
    } 

要考慮到使用變量prev在這個循環冗餘。

另外功能gets是不安全的，C標準不再支持。請使用功能fgets。