Coding project $6.$ Simulate an oversimplified predator$-$prey ecosystem.

The goal for this programming project is to simulate an oversimplified predator$-$prey ecosystem. Specifically, this ecosystem contains only two organisms, one being the prey and the other the predator. For the ease of reference, I will name the preys Zoomies and predators Swoopies. $($Note that you can name them differently in your project.$)$

Specifically, Zoomies and Swoopies live in a world composed of a $30$ x $30$ grid of cells. Only one critter may occupy a cell at a time. The grid is enclosed, so a critter is not allowed to move off the edges of the world. Time is simulated in time steps. Each critter performs some action at every time step.

The Zoomies behave according to the following model:

Move. At every time step, randomly try to move up$,$ down, left, or right. If the neighboring cell in the selected direction is occupied or would

move the Zoomie off the grid, then the Zoomie stays in the current cell.

Breed. If a Zoomie survives for three time steps, then at the end of the time step $($that is$,$ after moving$)$ the Zoomie will breed. This is simulated by creating a new Zoomie in an adjacent $($up$,$ down, left, or right$)$ cell that is empty. If there is no empty cell available, then no breeding occurs. Once an offspring is produced, a Zoomie cannot produce an offspring until three more time steps have elapsed.

The Swoopies behave according to the following model:

Move. Every time step, if there is an adjacent Zoomie $($up$,$ down, left, or right$),$ then the Swoopie will move to that cell and eat the Zoomie. Otherwise, the Swoopie moves according to the same rules as the Zoomies. Note that a Swoopie cannot eat other Swoopies.

Breed. If a Swoopie survives for eight time steps, then at the end of the time step it will spawn off a new Swoopie in the same manner as the Zoomie.

Starve. If a Swoopie has not eaten a Zoomie within the last three time steps, then at the end of the third time step it will starve and die. The

Swoopie should then be removed from the grid of cells.

During one turn, all the Swoopies should move before the Zoomis do$.$

Write a program to implement this simulation and draw the world using two different ASCII characters, for example, an $"$o$"$ for a Zoomie and an $"$x$"$ for a Swoopie. Create a class hierarchy with the base class Organism $($shown below$)$ and two derived classes Zoomie and Swoopie. The World class sets up this small ecosystem.

class Organism

$\{$

friend class World; $//$ Allow world to affect organism

public:

Organism$()$;

Organism$($World $*$world$,$ int x$,$ int y$)$;

~Organism$()$; $//$Ask yourself: should this function be declared virtual?

virtual void breed$()=0$; $//$ Whether or not to breed

virtual void move$()=0$; $//$ Rules to move the critter

virtual int getType$()=0$; $//$ Return if Swoopie or Zoomie

virtual bool starve$()=0$; $//$ Determine if organism starves

protected:

int x$,$y; $//$ Position in the world

bool moved; $//$ Bool to indicate if moved this turn

int breedTicks; $//$ Number of ticks since breeding

World $*$world;

$\}$;

class World

$\{$

friend class Organism; $//$ Allow Organism to access grid

friend class Swoopie; $//$ Allow Organism to access grid

friend class Zoomie; $//$ Allow Organism to access grid

public:

World$()$;

~World$()$;

Organism$*$ getAt$($int x$,$ int y$)$; $//$return a pointer to the critter at position $[$x$][$y$]$

void setAt$($int x$,$ int y$,$ Organism $*$org$)$;

void Display$()$; $//$display the grid

void SimulateOneStep$()$; $//$simulate one step

private:

Organism$*$ grid$[$WORLDSIZE$][$WORLDSIZE$]$; $//$WORLDSIZE$=30$

$\}$;

Initialize the small world with $5$ Swoopies and $100$ Zoomies. After each time step, prompt the user to press Enter to move to the next time step. You should be able to observe a cyclical pattern between the population of predators and prey, although random perturbations may lead to the elimination of one or both species.

Demonstration:

Each learner will demonstrate your project by first compile it and then run it for $50$ time steps.

Submission: concatenate the following files into one PDF file.

DesignDoc: describe the algorithm of your World::SimulateOneStep$()$ function.

Organism.h

Organism.cpp

world.h

world.cpp

Zoomie.h

Zoomie.cpp

Swoopie.h

Swoopie.cpp

main.cpp