Structure Linked Lists: Searching for Words.

[chucker]

So a user inputs an artist name, and then if the input matches one of the nodes containing the artist names i need to return that. but then also if the input does not match any of the nodes, I need to insert a new one. I have some lame attempt below, any guidance to fix it up would be fantastic. This is to be written in C

Also my structure that this function goes off of is shown below as well.

 
artistNodePtr findOrInsertArtist( artistNodePtr *sPtr, char *artistID ) {

artistNodePtr newNodePtr;
temp = sPtr

if(temp->artistName_p == artistID){
  return temp 
}else{
  newNodePtr = (artistNodePtr) malloc(sizeof(sPtr)

}
}

struct artist {
  char *artistName_p;
  struct disc *disc_p;
  struct artist *nextArtist_p;
};

typedef struct artist artist_t;
typedef struct artist *artistNodePtr;

[Paul McKenzie]

So a user inputs an artist name, and then if the input matches one of the nodes containing the artist names i need to return that. but then also if the input does not match any of the nodes, I need to insert a new one.

So where is your basic linked list code? The code to add, search, etc. I don't see any. That is the code you should be working on.

If you had that code, then this function you described above is very easy. Just call the functions that performs the actions you described:

artistNodePtr addName(const char *name)
{
   artistNodePtr ptr = NULL;
   ptr = findArtistName( name );
    if ( !artistNodePtr )
       artistNodePtr = insertNameInList( name );
   return artistNodePtr;
}

But again, if the foundation doesn't work, then code such as above doesn't work.

Regards,

Paul McKenzie

[chucker]

shoot. Well you are not going to like it, you helped me before and said my set up was excessive, but it was also given to me by the proffessor :/ so it is what it is. here is the entirety again

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


#define LINEBUFFERSIZE 256


/* Definitions for data structure nodes (artist, disc, track)  */


struct song {
  char *songName_p;
  int trackNumber;
  struct song *nextSong_p;
};

struct disc {
  char *discName_p;
  int year;
  struct song *song_p;
  struct disc *nextDisc_p;
};

struct artist {
  char *artistName_p;9i
  struct disc *disc_p;
  struct artist *nextArtist_p;
};

typedef struct artist artist_t;
typedef struct disc disc_t;
typedef struct song song_t;

typedef struct artist *artistNodePtr;
typedef struct disc *discNodePtr;
typedef struct song *songNodePtr;

/* function  prototypes */


artistNodePtr findOrInsertArtist( artistNodePtr *sPtr, char *artistID );


discNodePtr  findOrInsertDisc(discNodePtr *sPtr, char *discID, int releaseYear);


void  findOrInsertSong(songNodePtr *sPtr, char *songID, int trackID);


void getNextLine(char buffer[], int bufferSize, FILE *fptr);


/* May need more function prototypes here */


int main(int argc, char *argv[]) {


   char lineBuffer[LINEBUFFERSIZE];
   artistNodePtr startPtr = NULL; 
   FILE *musicFile;
   char *artistTemp, *discTemp, *yearTemp, *trackTemp, *songTemp;
   int year, track;
   artistNodePtr theArtist;
   discNodePtr theDisc;

  if(argc==1) {
      printf(" Must supply a file name as command line argument/n");
      return 0;
   }

  if((musicFile = fopen(argv[1], "r")) == NULL) {
      printf ("Error opening music file.  Program terminated/n");
      return 0;
   }

  getNextLine(lineBuffer, LINEBUFFERSIZE, musicFile);
   while(!feof(musicFile)) {


      artistTemp = strtok(lineBuffer,";");
      if (artistTemp == NULL) {
        printf("Error analyzing  input txt file; Program is terminated\n");
        return 0;
      }
      discTemp = strtok(NULL ,";");
      if (discTemp == NULL) {
        printf("Error analyzing input txt file; Program is terminated\n");
        return 0;
      }
      yearTemp  = strtok(NULL ,";");
      if (yearTemp == NULL) {
        printf("Error analyzing input txt file; Program is terminated\n");
        return 0;
      }
      trackTemp = strtok(NULL ,";");
      if (trackTemp == NULL) {
        printf("Error parsing input file; Program is terminated\n");
        return 0;
      }
      songTemp = strtok(NULL ,"\n");
      if (songTemp == NULL) {
        printf("Error parsing input file; Program is terminated\n");
        return 0;
      }

      /* convert the year and track strings to integers using the C atoi() function */
      year = atoi(yearTemp);
      track = atoi(trackTemp);

      theArtist = findOrInsertArtist(&startPtr, artistTemp);
      theDisc = findOrInsertDisc(&(theArtist->disc_p), discTemp, year);
      findOrInsertSong(&(theDisc->song_p), songTemp, track);

      getNextLine(lineBuffer, LINEBUFFERSIZE, musicFile);
  }  

  /* database display code somewhere here */


  } 

artistNodePtr findOrInsertArtist( artistNodePtr *sPtr, char *artistID ) {

artistNodePtr newNodePtr;
temp = sPtr

if(temp->artistName_p == artistID){
  return temp 
}else{
  newNodePtr = (artistNodePtr) malloc(sizeof(sPtr)



}  

discNodePtr findOrInsertDisc( discNodePtr *sPtr, char *discID, int releaseYear) {


} 

void findOrInsertSong(songNodePtr *sPtr, char *songID, int trackID) {

}  

void getNextLine(char buffer[], int bufferSize, FILE *fptr) {


  char temp;
  int i = 0;

  buffer[0] = fgetc(fptr);
  while ( (!feof(fptr)) && (buffer[i] != '\n') &&  i<(bufferSize-1)) {
    i = i +1;
    buffer[i]=fgetc(fptr);
  }


  if ((i == (bufferSize-1)) && (buffer[i] != '\n')) {
    temp = fgetc(fptr);
    while (temp != '\n') {
      temp = fgetc(fptr);
    }
  }

  buffer[i] = '\0';
}

[chucker]

Maybe im missing what you mean by the basic linked list code. eh its in there right :/

[chucker]

added some code for creating the new node if it doesnt exist already. step in the right direction ?

 

artistNodePtr findOrInsertArtist( artistNodePtr *sPtr, char *artistID ) {

   artistNodePtr newNodePtr;
   
   temp = sPtr


if(temp->artistName_p == artistID){
return temp 
}  else{

artistNodePtr newNodePtr = (artistNodePtr)malloc(sizeof(artist_t));
 
    if (newNodePtr != NULL) {           
 
        newNodePtr->artistName_p = (char*)malloc((strlen(artistID)+1)*sizeof(char));
 
        if (newNodePtr->artistName_p != NULL) {  
 
            strcpy(newNodePtr->artistName_p, artistID);
 
        }
 
        newNodePtr->nextArtist_p = NULL;
 
        newNodePtr->disc_p = NULL;
 
    }

[Alterah]

Let's say I have a linked list of numbers. Basic operations on this list would be to insert a number, delete a number, and find a number. Let us also suppose I impose the restriction that the list must be sorted and the numbers unique. Well, before any insert operation I would need to first see if that number is in the list. If so, the quit. Otherwise I proceed with the insert, making sure to insert at the correct "index" such that the new list is still sorted.

This is what Paul is getting at. Forget about being specific and trying to do all the work in one function. Break down the operations you need into smaller functions. A find function simply needs to start at the head of your list, and go through comparing the data items with a passed in key and then return a pointer to the correct node if it exists.

[chucker]

k i need to make a new function like so then?:

artistNodePtr FindArtist( artistNodePtr *sPtr, char *artistID); {

(pseudo)

while sptr != null

if sptr -> data = artistID
return sptr
else sptr -> nextartist_p

[Alterah]

I think adding such a function makes sense. I assume you mean:

(more C-ish pseudocode :P)
while sptr != null
    if sptr -> data == artistID
        return sptr
    else 
        sptr = sptr -> nextartist_p 

[chucker]

thank u. aah, do i need to use the strcmp function since im dealling with letters of a word too? or no?

[Alterah]

That depends, if you have a unique integer ID for the artists, you can use ==. Otherwise, if you are trying to compare the actual name, then you will need to use strcmp. Of course, if this was C++ and you were using the string class, then == would work as expected.

[chucker]

would this be how to strcmp:

artistNodePtr FindArtist( artistNodePtr *sPtr, char *artistID); {



while (artistNodePtr != NULL){
    if (strcmp(sPtr ->artistName_p == artistID)){
        return artistNodePtr;
}
    else{
        artistNodePtr = artistNodePtr-> nextArtist_p;

[Paul McKenzie]

would this be how to strcmp:

No. Are you reading the documentation on the strcmp() function, or just guessing how it's used?

Some advice:

If you have a question concerning how a function such as strcmp() works, why not just write a tiny main() program to test how it works?

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

int main()
{
    int retVal = strcmp("abc", "123");
    printf("The value of strcmp when I compared is &#37;d\n", retVal);
    retVal = strcmp("abc", "abc");
    printf("The value of strcmp when I compared is %d\n", retVal);
    retVal = strcmp("123", "abc");
    printf("The value of strcmp when I compared is %d\n", retVal);
}

That is how programmers who do not know how a function works goes about learning how it works -- by writing small programs such as above.

The strcmp() function takes two arguments and returns a value depending on whether the value are less than, greater, or equal to each other.

Regards,

Paul McKenzie

[chucker]

Okay so I tried doing strcmp correctly after reading about it, but its giving the error: request for member 'artistName_p' in something not a structure. i mean it is a part of the structure, so why does it not work? I guess the way i have my program set up i need to use another method besides strcmp?

artistNodePtr findOrInsertArtist( artistNodePtr *sPtr, char *artistID ) {

   char name[20];

   printf("enter an artist name");
   scanf("%s", &name);

   artistID = name;

   while (sPtr != NULL){
    if (strcmp(artistID, sPtr->artistName_p)==0){

[Alterah]

The problem is not with strcmp, but with your typedef usage.

artistNodePtr findOrInsertArtist( artistNodePtr *sPtr, char *artistID )

[chucker]

crap. This format they gave us to work with... kinda wish i just went and did my own thing instead. Lol have any alternatives or ways to make it work? Like i could i just erase the typedef and would it still work? Or how about throwing "typedef struct artist *artistNodePtr;" into the struct instead of typedefing it