Creating a Linked List from File Input - c

Question

Basically what I'm trying to do is take in a txt file and create a linked list off of it. The txt file contains either a "i" or "d" followed by a space and then a number.
Example of txt file:
i 10
i 12
d 10
i 5
I am trying to take in the input file and based off the input create a linked list. If the letter is an "i", I am trying to add it to the linked list. If it is a "d", I am trying to delete it from the list.
This is what I have so far. I have taken in the file and read it line by line, separating the letters from the number and stores them in char pointers. I tried earlier to create a linked list but it did not work out properly. Could someone please point me in the right direction on where and how I should implement the linked list.
#include<stdio.h>
#include<stdlib.h>
#include <ctype.h>
#include <string.h>
struct node { // creation of node structure
int data; // data inside node
struct node *next; // address to the next node int the list
};
void Insert (struct node *root, int x){ // this method will insert a node into the linked list
struct node *newnode;
newnode = (struct node*)malloc(sizeof(struct node));
newnode->data=x;
newnode->next = NULL; // this creates the node and stores the input into the data variable
if (root == NULL){ // if the root node is empty, point the root node to this pointer.
root = newnode;
}
else {
newnode->next=root; // if the link list is not empty, set whatever head point was pointing to previously equal to newnode-> next
root=newnode; // now make the head node point to the newnode
}
}
void printlist(struct node *root)
{
struct node *temp;
temp=root;
while(temp!=NULL)
{
printf("%d",temp->data);
temp=temp->next;
}
printf("\n");
}
int main (int argc, char *argv[]){
// Need to create a Root Node
struct node *root;
if (argc != 2) { // if the input is more than one, error
return EXIT_FAILURE;
}
// argv[1] will contain the file name input.
FILE *file = fopen(argv[1], "r");
// we need to make sure the file is not empty, error case.
if (file == NULL){
printf("error\n");
exit(0);
}
// if the file is empty, print an empty line. ******** MAKE SURE TO COME BACK TO THIS ************
char linestring[BUFSIZ]; // this will hold our file input after we read/scan it.
// now we need to read the file
while (fgets(linestring, sizeof(linestring), file)) // reads the entire file until it hits Null
{
// need to split up the lines so that we separate letters from integars.
// look for \t or " " and use strtok.
char* letter = strtok(linestring, " \t\n"); // stores the letter from the line
char* number = strtok(NULL, " \t\n"); // stores the numbers from the line
// now we need to now check the letter and see whether it is an "i" or a "d"
// use sting compare (it returns a 0 if the letter is equal to what we are checking)
if (strcmp(letter, "i") == 0){ // This checks the letter and if it is "i", we are going to be inserting a node
// need to create the new node to be inserted and assign the number value to it.
int x;
x = atoi(number); // converts the string input into a integar
Insert(root, x); // method which inserts the input onto the linked list.
}
if (strcmp(letter, "d") == 0){ // This checks the letter and if it is "d", we are going to be deleting a node
}
}
printlist(root);
fclose(file);
}

Answer 1

I assume that values does not repeated.
struct node
{ // creation of node structure
int data; // data inside node
struct node *next; // address to the next node int the list
};
//insertion in last
int insertNode(node **root, node *data)
{
if(!data) return 0;
//check if root available. if not data will be the root
if(!*root)
{
*root = data;
data->next = NULL;
return 1;
}
node *temp = *root;
while(temp->next)
{
temp = temp->next;
}
temp->next = data;
return 1;
}
//deletion. if multiple ocures first will delete
int deleteNode(node **root, int num)
{
if(!root) return 0;
node *temp = *root;
if(temp->data == num)
{
if(temp->next)
{
*root = temp->next;
}
free(temp);
return 1;
}
while(temp->next)
{
node* deleteThis = temp->next;
if((temp->next->next) && temp->next->data == num)
{
//delete next
temp->next = temp->next->next;
free(deleteThis);
return 1;
}
else if(temp->next->data == num)
{
//the last node
temp->next = NULL;
free(deleteThis);
return 1;
}
temp = temp->next;
}
return 0;
}
int main(int argc, char *argv[]){
//make root node
node* root = NULL;
// if the input is more than one, error
if (argc != 2) return EXIT_FAILURE;
// argv[1] will contain the file name input.
FILE *file = fopen(argv[1], "r");
// we need to make sure the file is not empty, error case.
if (file == NULL)
{
printf("error\n");
exit(0);
}
// if the file is empty, print an empty line.
/*int size = ftell(file);
if (size == 0){
printf("\n");
}
printf("%d",size);*/
char linestring[BUFSIZ]; // this will hold our file input after we read/scan it.
// now we need to read the file
while (fgets(linestring, sizeof(linestring), file)) // reads the entire file until it hits Null
{
// printf("%s", linestring); // stores each line into linestring.
// need to split up the lines so that we separate letters from integars.
// look for \t or " " and use strtok.
char* letter = strtok(linestring, " \t\n"); // stores the letter from the line
char* number = strtok(NULL, " \t\n"); // stores the numbers from the line
//changed from here
int n =atoi(number);//convert string to int
if(*letter == 'i')
{
//creates node to be inserted
node *data = NULL;
data = (struct node*)malloc(sizeof(node));
data->data = n;
data->next = NULL;
if(!insertNode(&root,data)) //if insertion gose wrong 0 will return
printf("insert %s was faild\n", number);
}
else
{
if(!deleteNode(&root,n))
printf("Couldnt Delete (%s not in the list)\n )", number);
}
}
}

Answer 2

**FULL WORKING CODE IN C++ FOR REFERENCE**
#include<bits/stdc++.h>
#include<fstream>
using namespace std;
struct node{
int data;
struct node* next;
};
typedef struct node node;
typedef struct node* nodeptr;
nodeptr Create(nodeptr head,nodeptr &current,int x){
nodeptr temp = (nodeptr)malloc(sizeof(node));
temp->next=NULL;
temp->data=x;
if(current==NULL){
current=temp;
head=temp;
}
else{
current->next=temp;
current=temp;
}
return head;
}
nodeptr Delete(nodeptr head, int x){
nodeptr temp = head;
nodeptr temp1;
while(temp->data!=x){
temp1=temp;
temp=temp->next;
}
temp1->next=temp->next;
free(temp);
temp=NULL;
return head;
}
void PrintC(nodeptr head){
nodeptr temp = head;
while(temp!=NULL){
cout<<temp->data<<" ";
temp=temp->next;
}
}
int main(){
nodeptr current = NULL;
nodeptr head = current;
string str;
ofstream myfile;
myfile.open("file.txt",ios::out);
myfile << "i 1 i 2 i 3 i 4 i 5 d 2 d 3";
myfile.close();
ifstream myfile1("file.txt");
getline(myfile1,str);
myfile1.close();
int i=0;
while(str[i]!='\0'){
if(str[i]!=' '){
if(str[i]=='i'){
int n = str[i+2]-48;
head=Create(head,current,n);
i=i+2;
}
else if(str[i]=='d'){
int n = str[i+2]-48;
head = Delete(head,n);
i=i+2;
}
}
i++;
}
cout<<endl;
PrintC(head);
return 0;
}