Question

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


int main(int argc, char** argv) {

    Book * dummy = newBook("dummy", "dummy", 00000);

    printf("%s %s %ld", dummy->title, dummy->author, dummy->ISBN);

    dummy->next = NULL;


    Book* newishBook = newBook("Foo", "Chris", 1234);
    insertToList(newishBook, dummy);

    Book* another = newBook("Bar", "Jim", 23344);
    insertToList(another, dummy);

    Book* yet = newBook("Derp", "Bob", 999);
    insertToList(yet, dummy);

    displayList(dummy);

    searchISBN(999);

    return (EXIT_SUCCESS);
}

Book* newBook(char* newTitle, char* newAuthor, long newISBN) {
    Book* new_book = malloc(sizeof(Book));

    strcpy(new_book->title, newTitle);
    strcpy(new_book->author, newAuthor);
    new_book->ISBN = newISBN;
    return new_book;
}



void insertToList(Book* bookToInsert, Book* dummy){
    Book* currentNode = dummy;
    Book* temp = malloc(sizeof(Book));

    if (currentNode->next == NULL){
        currentNode->next = bookToInsert;
        printf("Head");
    } else {
        currentNode= currentNode->next;        
        while(currentNode->ISBN > bookToInsert->ISBN){

            if (bookToInsert ->ISBN < currentNode->ISBN){
                // if isbn of current book more than current node, move to next current node
                //otherwise add here
                printf("Added");
                temp->next = currentNode->next;
                bookToInsert->next = currentNode->next;
                currentNode->next = temp->next;
            }
        }
    }
}

void displayList(Book* dummy){
    //start at dummy node-
    Book* currentNode = dummy;
    bool run = true;

    //print until next = null
    while(run==true){
        if (currentNode->next != NULL){
            printf("%s %s %ld \n", currentNode->title, currentNode->author, currentNode->ISBN); 
            currentNode = currentNode ->next;
        } else {
            run = false;
        }
    }    
}

此程序旨在创建作为链接列表节点的书籍结构。书籍在头文件Book.h中定义如下：

#ifndef BOOK_H
#define BOOK_H

#ifdef  __cplusplus
extern "C" {
#endif


typedef struct book_t {
    char title[50];
    char author[30];
    long ISBN;
    struct Book *next;
} Book;

Book* newBook(char* newTitle, char* newAuthor, long newISBN);

#ifdef  __cplusplus
}
#endif

#endif  /* BOOK_H */

我觉得我的insertToList函数已经接近工作了，但是从错误的角度来看，我已经失去了代码盲目性，而且我确信它有一些非常基本的错误。目前没有输出 - 只是一个空的终端，我相信循环没有正常退出。取消注释printf语句“added”和“head”会导致程序无限循环，输出“添加”到终端。

Answer 1

insertToList函数不处理所有情况。

首先检查列表是否为空（正确） while循环开始缺少逻辑。你应该：

1) check if currentNode is larger (same as your if statement)
  a) if it is smaller, insert the book,
  b) if it is larger, you need another check:
      i) if currentNode has next !== NULL, move down and repeat loop
      ii) if next == NULL, add book at the end and return;

Answer 2

结构应该是：

typedef struct Book {
    char title[50];
    char author[30];
    long ISBN;
    struct Book *next;
} Book;

代码可以是：

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

Book *newBook(char *newTitle, char *newAuthor, long newISBN);
void displayList(Book *dummy);
void insertToList(Book *bookToInsert, Book *dummy);
void freeList(Book *head);

int main(void)
{
    Book *dummy = newBook("dummy", "dummy", 00000);

    printf("%s %s %ld\n", dummy->title, dummy->author, dummy->ISBN);

    printf("Newish\n");
    Book *newishBook = newBook("Foo", "Chris", 1234);
    insertToList(newishBook, dummy);
    displayList(dummy);

    printf("Another\n");
    Book *another = newBook("Bar", "Jim", 23344);
    insertToList(another, dummy);
    displayList(dummy);

    printf("Yet\n");
    Book *yet = newBook("Derp", "Bob", 999);
    insertToList(yet, dummy);
    displayList(dummy);

    //searchISBN(999);
    freeList(dummy);

    return(EXIT_SUCCESS);
}

Book *newBook(char *newTitle, char *newAuthor, long newISBN)
{
    Book *new_book = malloc(sizeof(Book));

    strcpy(new_book->title, newTitle);
    strcpy(new_book->author, newAuthor);
    new_book->ISBN = newISBN;
    new_book->next = NULL;
    return new_book;
}

void insertToList(Book *bookToInsert, Book *dummy)
{
    Book *currentNode = dummy;

    while (currentNode->next != NULL && currentNode->next->ISBN < bookToInsert->ISBN)
        currentNode = currentNode->next;
    bookToInsert->next = currentNode->next;
    currentNode->next = bookToInsert;
}

void displayList(Book *dummy)
{
    Book *currentNode = dummy;

    while (currentNode != NULL)
    {
        printf("%s %s %ld\n", currentNode->title, currentNode->author, currentNode->ISBN);
        currentNode = currentNode->next;
    }
}

void freeList(Book *head)
{
    Book *bp = head;
    while (bp != 0)
    {
        Book *bn = bp->next;
        free(bp);
        bp = bn;
    }
}

由于添加并使用了freeList()功能，这在valgrind下无泄漏。

注意添加每个条目后如何打印列表。这有助于确保正确构建列表。另请注意每行输出如何以换行结束。在打印换行符之前，您不一定会看到打印数据。特别是对于调试，请确保包含换行符 - 但即使不进行调试也通常是个好主意。

C-中的链接列表在排序位置添加结构

2 个答案: