Linked List confusion

[airj56]

/**
AUTHOR: Kevin Layfield
FILE: hw3.c
ASSIGNMENT: Homework 2
DATE: 9/14/2006
*/
#include <stdio.h>
#include <stdlib.h>
#include "hw3.h"
//initialization of a list.  program crashes here.  I don't know why.
void init_list(list_t *list){
     list->head=NULL;
     list->count=0;
     list->index=0;
     }
//add a new node to list
void add(list_t *list, int i, void *item)
{
     //node to be added
     node_t *newnode;
     //increment count
     list->count++;
     //assign the third argument as data for the node
     newnode->data=item;
     //if the list is empty, create a head
     if(list->count==0)
     {
          list->head = malloc(sizeof(node_t));
          list->head->data = newnode->data;
          list->head->next = NULL;
          
     }
     //else, traverse the list until desired position is reached
     else
     {
         list->traverse = list->head;
         while(list->index<i){
                        list->traverse=list->traverse->next;
                        list->index++;
                        }
         item = malloc(sizeof(node_t));
         //assign the new node's next value = to traverse's next value
         newnode->next = list->traverse->next;  
         //essentially place the newnode in the position ahead of traverse                     
         list->traverse->next = newnode;
         //reset index
         list->index=0;
     }
               
}

void *get(list_t *list, int i)
{
         void *returned;        
         list->traverse = list->head;
         //traverse list until you reach desired position
         while(list->index<i){
                        list->traverse=list->traverse->next;
                        list->index++;
                        }
         list->index=0;
         //assign the data value to a new variable
         returned = list->traverse->data;
         //return new variable
         return returned;
}

int size(list_t *list)
{
     //return the value that gets incremented each time a new node is added
     return list->count;
}

the .h file.....

typedef struct{
 void *info;
 void *next;
}node_t;


typedef struct{
  node_t  *front;
  int size;
}ll_t;

void init_ll(ll_t *l);

void add(ll_t *list, int i, void *item);
void *get(ll_t *list, int i);
int size(ll_t *list);

first off, i never used a linked list in C, only in Java and since its built into Util, it was a lot easier. Im trying to make a driver class in which i can put in any numbers i want, but i cant quite figure out how to do that, dont worry about the code above, i know its not all right, but i wanna fix it myself, just i have no idea where to go on the driver class. I know im gonna need a loop to go to the next node and keep gonig till the list is at its end. Thanks

[dwks]

BTW, there are no classes in C.

So you want to create a main() function that will test-drive your linked list? Something like this?

int main(void) {
    int x, i, c;

    for(x = 0; x < 10; x ++) {
        printf("Enter a number: ");
        while(scanf("%d", &i) != 1) {
            while((c = getchar()) != '\n' && c != EOF);
            printf("Invalid number, try again: ");
        }
        add_number(x);
    }

    for(x = 0; x < 10; x ++) {
        i = remove_last_number();
        printf("%d\n", i);
    }
}

[Tonto]

Your header file conflicts with the code file on several points

- typedef name of list structure
- wierd count variable
- wierd index variable
- really wierd transverse variable

If you're gonna fix those, then okay! Good things to watch out while you're doing so I s'pose.

[risby]

void init_list(list_t *list){
     list->head=NULL;
      list->count=0;
     list->index=0;
     }
//add a new node to list
void add(list_t *list, int i, void *item)
{
     //node to be added
     node_t *newnode;
     //increment count
      list->count++;
     //assign the third argument as data for the node
     newnode->data=item;
     //if the list is empty, create a head
      if(list->count==0)
      {
          list->head = malloc(sizeof(node_t));
          list->head->data = newnode->data;
          list->head->next = NULL;
          
     }
     //else, traverse the list until desired position is reached
     else

the malloc() will never be executed as count is being bumped to early.

[quzah]

There's no point in that malloc anyway, when all you have to do is assign "list->head = newnode", and be done with it.


Quzah.