COMP1511 Week 11 Tutorial Questions

Consider a Fruit Bot world with these 5 locations and a simulation lasting 4 turns:

Name Type Fruit Quantity Price
CSE Other
Drum Lab Buyer Pears 2 40
Vice Chancellors Garden Seller Pears 8 30
Power Plus Seller Electricity 684 2
Fruit Bin Anything 1000 1
Assume there is a single bot named Deckard who starts the simulation with $100 and battery level 48. Also assume Deckard has a maximum fruit kg of 7.
Deckard makes these actions in the 4 turns the simulation lasts.
1. Move 2
2. Buy 6
3. Move -1
4. Sell 6

Name	Type	Fruit	Quantity	Price
CSE	Other
Drum Lab	Buyer	Pears	2	40
Vice Chancellors Garden	Seller	Pears	8	30
Power Plus	Seller	Electricity	684	2
Fruit Bin	Anything		1000	1

List all the changes which occur in the Fruit Bot world each turn

How many times is fruit_bot.c run during each simulation.

What is its input?

What is its output (give examples)

How does a bot indicate whether it wishes to move East/West

The input to fruit_bot.c looks very complex, e.g.:

*** Fruit Bot Parameters ***
battery_capacity=74
maximum_fruit_kg=21
maximum_move=7

*** Turn 1 of 19 *** ***

CSE: other
Mathews A: will buy 1 kg of Apples for $51/kg
Quadrangle: other
Campus Charging: will sell 100 kJ of Electricity for $4/kJ
Kensington Apple Farm: will sell 3 kg of Apples for $18/kg
Campus Compost Heap: will buy 1000 kg of Anything for $1/kg
CLB 7: will buy 3 kg of Apples for $43/kg

"Botty McBotbot" is at "CSE" with $117, battery level: 64, 5 kg of Apples
"Buffalo McBuff" is at "Kensington Apple Farm" with $217, battery level: 74
"COMP1511 Student" is at "Campus Compost Heap" with $1, battery level: 24, 11 kg of Apples
*** You are "Botty McBotbot"

how do I read that in with scanf?

fruit_bot_input returns a pointer to this struct declared in fruit_bot.h

struct bot {
    char            *name;
    struct location *location;
    int             cash;
    int             battery_level;
    char            *fruit;
    int             fruit_kg;
    int             turns_left;
    int             battery_capacity;
    int             maximum_move;
    int             maximum_fruit_kg;
};

What do the fields mean.

What value can the fields take? If int can they be negative?, zero? If pointer can they be NULL?

A struct bot includes a pointer to this struct declared in fruit_bot.h

struct location {
    char                *name;
    char                *fruit;
    int                 price;
    int                 quantity;
    struct location     *east;
    struct location     *west;
    struct bot_list     *bots;
};

What do the fields mean.

What value can the fields take? If int can they be negative?, zero? If pointer can they be NULL?

What "non-fruit" values can the field fruit take?

Why is there a bots field in location structs?

Write a C function with this prototype:

int mars_bars_on_board(struct bot *b)

which given a pointer to a bot returns how many Mars Bars the bot has on board (yes Mars Bars are fruit)

Write a C function with this prototype:

int mars_bars_for_sale(struct bot *b)

which given a pointer to a bot returns how Mars Bars are for sale at the bot's current location

How do the struct used to represent locations in the Fruit Bot world differ from the linked lists you've seen in lectures?

What is tricky about circular lists ?

How can the lab exercises help with the assignment ?

Revision questions

The remaining tutorial questions are primarily intended for revision - either this week or later in session.

Your tutor may still choose to cover some of the questions time permitting.

C's sizeof operator is a prefix unary operator (precedes its 1 operand) - what are examples of other C unary operators?

Why is C's sizeof operator different to other C unary & binary operators?

Discuss errors in this code:

    struct node *a, *b, *c, *d;
    a = NULL:
    b = malloc(sizeof b);
    c = malloc(sizeof struct node);
    d = malloc(8);
    c = a;
    d.data = 42;
    c->data = 42;

The function member tests if a specified value is a found in a specified list, i.e. the function should return 1 if the value occurs in the list 0 otherwise. It has this prototype:

int member(int value, struct node *list);

Implement this function both iteratively (using a while/for loop) and recursively.

What does this code print

    int i;
    struct node *a[100];
    struct node *b = malloc(sizeof (struct node));
    b->data = 0;
    for (i = 0; i < 100; i = i + 1) {
        a[i] = b;
    }
    for (i = 0; i < 100; i = i + 1) {
        a[i]->data++;
    }
    printf("%d %d\n", a[0]->data, a[99]->data);

Name one advantage and one disadvantage of using a linked list compared to an array. Also state an example of when you would use an array over a linked list.