c - 错误: expected expression before 'book'

Question

我是一个 stackoverflow 浏览器，我正在学习第一门 C 类(class)。我已经为学校作业编写了一些代码大约一天了。我应该将一个节点插入到链表的中间。截至目前，我的大部分代码正在编译。我在使用我声明的函数之一时遇到错误:

bookshelves.c: In function ‘main’:
    bookshelves.c:53:14: error: expected expression before ‘book’
    print_shelf(book *head);
                ^~~~
bookshelves.c:62:14: error: expected expression before ‘book’
    print_shelf(book *head);
                ^~~~
bookshelves.c:66:14: error: expected expression before ‘book’
    print_shelf(book *head);
                ^~~~

我在代码中使用了3次声明的函数，但是函数的声明没有错误。我在网上找到的任何内容都不足以帮助我解决问题。我想我可能在函数声明或其他东西中使用了错误的变量，但改变它只会让我的代码更加困惑。

这是我的完整代码:

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

typedef struct book_struct {
    char *titles;
    struct book_struct *next;
} book;

void print_node(book *next);
void print_shelf(book *head);

int main()  {

    book *A = malloc(sizeof(book));
    book *B = malloc(sizeof(book));
    book *C = malloc(sizeof(book));
    book *D = malloc(sizeof(book));
    book *E = malloc(sizeof(book));

    A->titles = malloc(20);
    B->titles = malloc(20);
    C->titles = malloc(20);
    D->titles = malloc(20);
    E->titles = malloc(20);

    strcpy(A->titles, "War and Peace");
    A->next = NULL;

    strcpy(B->titles, "War on Drugs");
    B->next = NULL;

    strcpy(C->titles, "War ");
    C->next = NULL;

    strcpy(D->titles, "War Horse");
    D->next = NULL;

    strcpy(E->titles, "War of 1812");
    E->next = NULL;


    book *shelf = A;
    A->next = B;
    B->next = C;
    C->next = D;
    D->next = E;
    E->next = NULL; // always remember to set "next" of the last book to NULL

    printf("Bookshelf before inserting new book:\n");
    print_shelf(book *head);

    {
    book new_book;
    strcpy(new_book.titles, "Twilight");
    new_book.next = NULL;

    C->next = &new_book;
    new_book.next = C;
    print_shelf(book *head);
    }

    printf("Bookshelf after inserting new book:\n");
    print_shelf(book *head);

    return 0;
}

void print_node(book *next)  {
    printf("%c\n", *next->titles);
}

void print_shelf(book *head)  {
    book *current = head;

    while (current != NULL)  {
        print_node(current);

        //Advance current
        current = current->next;
    }
}

我尝试了不同的方法来修复该错误，但没有任何效果。希望您能提供有关该错误的帮助，您不必修复整个代码。一旦我克服了这个错误，我就可以从那里开始。

感谢您的帮助!

Answer 1

因此，您最初的错误是调用语法不正确，可以通过将 print_shelf(book *head); 更改为 print_shelf(shelf) 来纠正。我还重写了您的代码，以说明链表功能强大，并且不需要元素本身之外的每个元素的单独指针(我已经排除了释放元素，因为程序会无论如何立即终止):

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

typedef struct book_struct {
    char *titles;
    struct book_struct *next;
} book;

void add_node(book* head, book* newNode);
void print_node(book *next);
void print_shelf(book *head);

char* titles[] = {"War and Peace", "War on Drugs", "War ", "War Horse", "War of 1812" };

int main()  {

    book* head = malloc(sizeof(book));

    {
        book* currNode = head;
        int i = 0;
        for(; i < 4; ++i)
        {
            currNode->titles = malloc(20); 
            strcpy(currNode->titles, titles[i]); // malloc is technically not neccessary here, just for consistancy with your original code :)
            currNode->next = malloc(sizeof(book));
            currNode = currNode->next;
        }
        currNode->titles = malloc(20); 
        strcpy(currNode->titles, titles[i]);
        currNode->next = NULL;
    }   

    printf("Bookshelf before inserting new book:\n");
    print_shelf(head);

    {
        book* new_book = malloc(sizeof(book));
        new_book->titles = malloc(20);
        strcpy(new_book->titles, "Twilight");
        new_book->next = NULL;

        add_node(head, new_book);
    }

    printf("Bookshelf after inserting new book:\n");
    print_shelf(head);

    return 0;
}

void print_node(book *next)  {
    printf("%s\n", next->titles);
}

void print_shelf(book *head)  {
    book *current = head;

    while (current != NULL)  {
        print_node(current);

        //Advance current
        current = current->next;
    }
}

void add_node(book* head, book* newNode) {
    book* current = head;
    while(current->next) current = current->next;
    current->next = newNode;
}