Lecture 20:  Nested Data Structures

Content Tested:  Designing data structures

Lecture Content:

• Composite Data
• Arrays
• Records (structs)
• Nested Structs

Goals:

• Develop ability to apply principles and generalizations already learned to new problems and situations
• Develop problem-solving skills
• Prepare for transfer or graduate study
• Learn techniques and methods used to gain new knowledge in this subject

Assessment Technique:  Design Activity

Purpose:

Activity:

Scenario:  You work at a local video store that rents movies in the format of dvds and vhs video tapes.  Your manager, knowing that you have some programming experience, wants you to design a program to manage customer accounts, the dvd library, and the vhs movie library.  Up to this point, the video store keeps all records of customers on paper (an index card for each listing their account number, their name, their address, their telephone number, their current rentals, the the due dates of their videos).  When a customer rents one or more videos, the title, format, the rental price, and the due dates are written on their index card.  This is a small shop -- the store only has one copy of each movie per format, so when a video or dvd is returned they know exactly who rented the video.  Your manager wants you to design a program that will keep track of customer information and movie information.  In this activity, please design some data structures that you would use to keep track of appropriate information.  If you create a struct, please write the C code for the struct.  You do not need to write any functions -- just the data structures.  Try to incorporate nested data structures into your plan.  (Hint:  If you need some help, think of each vhs video or dvd being represented by a structure.)

Possible Solutions:

typedef struct{
    char first_name[MAX_NAME + 1]; /* lists first name of customer */
    char last_name[MAX_NAME + 1];  /* lists last name of customer */
    char street_address[MAX_ADDRESS + 1];  /* lists street address
                                              of customer */
    char city[MAX_CITY + 1];      /* lists city of address of customer */
    char state[3];                /* use postal abbreviation for state */
    int  telephone_number[10];    /* telephone number -- (xxx) xxx-xxxx */
    int  account_id;              /* unique account id for customer */
    movie  movie_rentals[MAX_RENTAL + 1];/* list of dvds currently rented by
                                            customer */
    double account_balance;       /* current account balance for customer */
} customer;

typedef struct{
    char title[MAX_TITLE + 1];   /* movie title */
    int year;                    /* year produced */
    char director[MAX_DIRECTOR + 1]; /* last name of director -- just
                                        in case 2
                                        movies have the same title */
    int format;                  /* 1 = dvd format, 2 = vhs format */
    int is_available;            /* 0 means that it is currently rented,
                                    1 means that it is available */
    double rental_price;         /* price to rent this video */
    date due_date;               /* if currently rented, this lists
                                    the due date,
                                    if not currently rented this lists the
                                    due date of the previous renter */
    int account_rented;          /* this is equal to the account number
                                    of the current renter, 0 otherwise
                                    (no person gets account id 0) */
} movie;

There would also be an array of movies containing every movie that the video store owns.  This array might store the movies in alphabetical order by title so that we could perform binary search on the array to locate a particular movie.

There would also be an array of customers containing every customer who has an account at the video store.  This array might store customer last names in alphabetical order so we could perform binary search on the array to locate a particular customer.  Or, one might want to store the customers in order according to their account id so when a movie is returned, the current id attached to the movie can be located quickly.
 

Possible Uses of Activity:

• Encourage students to work in groups and share their design with the rest of the class.   See how many designs are similar and describe strengths and weaknesses of the designs.
• Ask students how one might access the customer's last name in their particular design.  Also, if they didn't propose it in the original design, how would they store the collection of movies and the collection of customers?  The collection of customers is just like the collection of index cards that the store used before.