ENEE150 – 0102 ANDREW GOFFIN Linked List/Project 3

Intro to Linked Lists Essentially a more dynamic array! Goffin – ENEE150

Some Linked List Vocab Node  Each element in the list: stores data and a “next pointer” Head pointer  Points to first element in the linked list  Is NULL for an empty list Next pointer  Pointer in each node that indicates the next node in the list  Is NULL for the last element in the list Tail pointer (if applicable)  Points to last element in the linked list  Is NULL for an empty list Goffin – ENEE150

Defining a linked list Use a struct to define a single node in the list typedef struct node_type{ // type of data depends on application! int data1; float data2; // NEXT POINTER, SUPER IMPORTANT struct node_type *next; } node, *pnode; Goffin – ENEE150

Starting a linked list int main(void){ pnode head = NULL; head = (pnode)malloc(sizeof(node)); head->next = NULL; } A single node is allocated Next pointer is NULL, indicating that the node is the last (and only) node in the list Goffin – ENEE150

Project 3 Music server  Use dynamic data structures to store album, user, and playlist data Goffin – ENEE150

Project 3 - Albums Each album is a structure, and all albums can be stored as an array of structures  Each structure has three fields:  num_tracks – number of tracks on the album  tracks – array that stores track names  playlist_hits – array that stores number of hits each track gets Goffin – ENEE150

Project 3 – User Accounts A linked list of “account” structures  Add accounts dynamically to list  Each structure has an ID number, playlist linked list (see in two slides), and next pointer  The head pointer to the user’s playlist is what is stored in the struct – should be initialized to NULL Goffin – ENEE150

Appending to linked lists The last node in a linked list always has its next pointer set to NULL Simple concept: move through next pointers until you get to one that is NULL, and set that equal to your new node Example: append.c Goffin – ENEE150

Project 3 - Playlists Playlists are linked lists whose head pointers are in user structs Playlist struct has three fields:  album – stores album ID for track  track_num – track number on that particular album  next pointer for linked list Can retrieve track name using album, track_num, and the album array! Goffin – ENEE150

Other Project 3 Information You will take command line arguments for this project  An “album” file and a “transaction” file  The former stores album data, the latter stores “transaction” data  Transactions include: printing albums, modifying playlists, creating user accounts, etc.  Each transaction has a particular transaction ID Goffin – ENEE150