Question

I have used strtok to tokenize my input file and I need a linked list based on the output I got in the follwing format.

String:value-Next --> String:value-Next

I have the strings and values after I tokenized my file.

Here is my code:

FILE *pfi;
main(int argc, char* argv[])
{
    char string[1000], delim[] = " \n";
char *p;
    if(argc<2)
         {
          printf("entering format is wrong. compile program using gcc digraph.c and then enter it as ./a.out input.txt");
         }
    else if(argc == 2)
        {
         pfi=fopen(argv[1],"r");
        }
    if(!pfi)
         return 1;
while(fgets( string, sizeof(string)-1, pfi) != NULL)
     {
          p = string;
      p = strtok( string, delim );      

      while( p != NULL )
          {

               if (sscanf(p, "( %s  ",p)) printf("(\n"); 
            printf("%s\n", p);                    

           p = strtok( NULL, delim );                 
              }

         } fclose(pfi);


return 0;
}

The input file is in format:

A 20
B 30
C 40

Output is:

A
20
B
30
C
40

Please help me to create a linked list of format String:value-Next --> String:value-Next.

Answer 1

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

/* Create a struct to hold our data in the link list */
typedef struct node
{
   char value[100];
   int ivalue;
   struct node *next;
} Node_t;

void insertInList(Node_t **root, const char *value, int ivalue);
void printList(const Node_t *root);

int main(int argc, char *argv[])
{
   /* head of link list */
   Node_t *root=0;

   /* ignore this it is C++ - but its quicker to write an input method for it */
   bool done=false;
   while(!done)
   {
      /* ignore from here */
      std::string value;
      int ivalue=0;
      std::cout << "Enter value: " << std::flush;
      std::cin >> value;
      if(value.size() && value[0]=='q')
      {
         done=true;
         continue;
      }
      std::cout << "Enter ivalue: " << std::flush;
      std::cin >> ivalue;
      /* to here */
      insertInList(&root, value.c_str(), ivalue);
   }

   printList(root);
   /* Dont forget to free all the link list members after */

   return 0;
}

/* note head of list is passed as a pointer to a pointer so we can modify it */
void insertInList(Node_t **root, const char *value, int ivalue)
{
   Node_t *new_node=*root;
   Node_t *last_node=0;

   /* find the end of the list to insert to */
   while(new_node)
   {
      last_node=new_node;
      new_node=new_node->next;
   }

   /* reserve memory for new node */
   new_node=(Node_t *)malloc(sizeof(Node_t));
   /* copy data over */
   strncpy(new_node->value, value, sizeof(new_node->value)-1);
   new_node->ivalue=ivalue;
   new_node->next=0;
   if(last_node)
   {
      /* set previous node in list to point to our new node */
      last_node->next=new_node;
   }
   else
   {
      /* corner case for first element in list */
      *root=new_node;
   }
}

void printList(const Node_t *root)
{
   const Node_t *node=root;

   while(node)
   {
      printf("%s %d\n", node->value, node->ivalue);
      node=node->next;
   }
}