【发布时间】：2014-02-18 07:53:33
【问题描述】：
我需要创建一个带有哨兵节点的循环双向链表，该节点应该从文件中读取数据并将其插入列表中，而不是对其执行一些操作。现在我被困在一个简单的打印功能上，由于某种原因它不会从列表中打印出来。文件中的数据是字符串的形式， 例如：“流行的排序算法， 冒泡排序、归并排序、“空行”等
到目前为止，这是我的代码：
头文件包含：
typedef struct NODE {
struct NODE *prev;
char *value;
struct NODE *next;
} NODE;
typedef struct LIST {
int count;
struct NODE *next;
struct NODE *prev;
} LIST;
int InsertEnd(NODE *head, char * value, int *lineCount);
void printLines(int *lineCount);
void Traverse(NODE *head);
主要包含：
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include "header.h"
int main()
{
int lineCount = 0;
NODE *head;
head = (NODE *)malloc(sizeof(NODE)); /* creates head node dynamically */
head->next = NULL; /* points to first element */
head->prev = NULL; /* points to last element */
head->value = "HEAD"; /* not needed, but it was pretty useful when debugging */
//*********BEGIN OF OPEN FILE FUNCTION
FILE* fp;
char *fname = NULL;
fname = (char *)malloc(200); <<<<<===== I would prefer to set the size dynamically adjusting but I dont know how
printf("Reading file input.txt\n");
//Checks if the file us unable to be opened, then it shows the error message
if ( !(fp = fopen("input.txt", "r")))
{
printf("\nError, Unable to open the file for reading \n");
exit(100);
}
//*********BEGIN OF READ FROM FILE FUNCTION
while (!feof(fp))
{
fgets(fname, 150, fp); //reads the file and stores in buffer
fname[strlen(fname) - 1] = '\0'; // reduces empty strings for input
if (fname != '\0')
{
InsertEnd(head, fname, &lineCount);
//printf("%s\n", head->next->value); <<<<==== If uncomment this print function would work properly but only in this context
}
else
{
printf("Error'\n"); // For debugging
}
}
Traverse(head); // Print Function Should Be Working in Here
printf("Debugging print\n");
printLines(&lineCount); // Shows Line Count
return 0;
}
// Function inserts a new node at the end of the LIST
int InsertEnd(NODE *head, char * value, int* lineCount)
{
int lineCounter = *lineCount;
/* create new node */
NODE *newnode;
newnode = (struct NODE *)malloc(sizeof( struct NODE));
newnode->value = value;
/* placing new node in LIST */
if (head->next == NULL) /* LIST was empty */
{
newnode->next = head;
newnode->prev = head;
head->next = newnode;
head->prev = newnode;
lineCounter++; // Increment line counter
}
else /* LIST wasn't empty */
{
newnode->next = head;
newnode->prev = head->prev;
head->prev->next = newnode; /* adjust node that was previously last */
head->prev = newnode; /* adjust head node */
lineCounter++; // Increment line counter
}
*lineCount = lineCounter;
return lineCount;
}
// This function prints how many lines there are in the LIST, but I need to get rid of the empty spaces
void printLines(int *lineCount)
{
printf("Line counter is %d", *lineCount); // Shows the number of lines, but doesn't skip empty ones.
}
void Traverse(NODE *head)
{
NODE *current = head;
printf("Forward:");
while (current!= head->prev)
{
printf("%s \n", current->value);
current = current->next;
}
printf("\n");
}
因此，到目前为止，我有几个问题：
1) 我很可能需要删除列表中的空字符串。什么是更好的方法，在阅读时摆脱它们或在打印时不显示？我该怎么做呢？
2) 如何修复我的 print(traverse) 功能以及那里出了什么问题？
3) 此外，所有这些都应该通过菜单管理器进行，它会提示输入命令（我认为这是对的）。但是有些功能我不知道如何实现。例如，当使用点击“I”时，它应该调用插入函数并提示用户输入另外两个值和，然后在适当的位置插入。我该怎么做？示例“I 1 8”
4) 与上一个类似，应该有 List 函数，它应该打印特定值之间的行。用户输入格式应为“L to”列表（含）。示例“L 2 5”
5) 与前面类似，应该有一个包含“D”格式的删除函数。示例“D 3 7”
6) 最后是“S”格式的保存功能示例“S output.txt”
感谢您的帮助！
【问题讨论】：
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您可以将此添加到您的待处理事项列表中：
while (!feof(fp))is wrong。并且确保fgets()在假设它工作之前完全未检查潜在故障。
标签： c linked-list