I need to create a circular doubly linked list with a sentinel node which is supposed to read data from a file and insert it in the list, than perform some operations with it. For now I'm stuck on a simple print function which won't print from a list for some reason. The data in the file is in the form of strings, example: "Popular Sorting Algorithms, Bubble Sort, Merge Sort, "empty line", etc
Here is my code so far:
Header file contains:
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);
Main contains:
#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");
}
Therefore, I have several problems so far:
1) I need to get rid of empty strings in my list most likely. What would be a better approach, to get rid of them while reading or just not displaying when printing? How would I do this exactly?
2) How can I fix my print(traverse) function and whats wrong there?
3) Additionally all of this should be going on through the menu manager which would prompt for a command ( I got this right I think). But there are some functions that I don't know how to implement. For example when used hits "I" it should call Insert functions and prompt the user to enter two more values and , and later insert at the appropriate . How would I do that? Example "I 1 8"
4) Similarly to the previous one, there should be List function which should print lines between specific values. User input format should be "L to " list inclusively. Example "L 2 5"
5) Similarly to previous there should be a delete function with the format "D " inclusively. Example "D 3 7"
6) And the very last is the Save function in the format "S " Example "S output.txt"
Thank You for the help!
