Computer Science/61b/Projects/Ocean/Ocean.java
< Computer Science | 61b | Projects | Ocean
- This page contains computer code. Unlike all articles on the lensowiki, which are released under the GFDL, this code is released under the GPL.
Copyright 2006, 2007 Paul Borokhov. All rights reserved.
This code is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
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/* Ocean.java */
/**
* The Ocean class defines an object that models an ocean full of sharks and
* fish. Descriptions of the methods you must implement appear below. They
* include a constructor of the form
*
* public Ocean(int i, int j, int starveTime);
*
* that creates an empty ocean having width i and height j, in which sharks
* starve after starveTime timesteps.
*
* See the README file accompanying this project for additional details.
*/
public class Ocean {
/**
* Do not rename these constants. WARNING: if you change the numbers, you
* will need to recompile Test4.java. Failure to do so will give you a very
* hard-to-find bug.
*/
public final static int EMPTY = 0;
public final static int SHARK = 1;
public final static int FISH = 2;
/**
* Define any variables associated with an Ocean object here. These
* variables MUST be private.
*/
private int x;
private int y;
private int starvetime;
private int[] cells;
private int[] hunger;
/**
* The following methods are required for Part I.
*/
/**
* Given an x & y coordinate, returns the cell's index in an ocean array
* if either coordinate is out of bounds due to the ocean's size, convert it accordingly
* @param x is the x-coord; @param y is the y-coord of the cell
* @return the index in the array
**/
public int cellind(int x, int y) {
x = x%this.x; // Math.abs(x)%this.x; gives incorrect values
y = y%this.y;
if (x < 0) { x = x+this.x; }
if (y < 0) { y = y+this.y; }
int ind = this.x*y+x;
return ind;
}
/** @param pos is the index in the ocean array
the methods below convert an array index into an x and y coordinate, respectively **/
public int coordx(int pos) {
int i = pos%x;
return i; }
public int coordy(int pos) {
int j = pos/x;
return j; }
/**
* Ocean() is a constructor that creates an empty ocean having width i and
* height j, in which sharks starve after starveTime timesteps.
* @param i is the width of the ocean.
* @param j is the height of the ocean.
* @param starveTime is the number of timesteps sharks survive without food.
*/
public Ocean(int i, int j, int starveTime) {
x = i;
y = j;
starvetime = starveTime;
cells = new int[i*j];
for (int ic=0; ic<cells.length; ic++) { cells[ic] = EMPTY; } // all cells EMPTY by default
hunger = new int[i*j];
for (int ih=0; ih<hunger.length; ih++) { hunger[ih] = 0; } // hunger of all cells 0 by default
}
/**
* width() returns the width of an Ocean object.
* @return the width of the ocean.
*/
public int width() {
return x;
}
/**
* height() returns the height of an Ocean object.
* @return the height of the ocean.
*/
public int height() {
return y;
}
/**
* starveTime() returns the number of timesteps sharks survive without food.
* @return the number of timesteps sharks survive without food.
*/
public int starveTime() {
return starvetime;
}
/**
* addFish() places a fish in cell (x, y) if the cell is empty. If the
* cell is already occupied, leave the cell as it is.
* @param x is the x-coordinate of the cell to place a fish in.
* @param y is the y-coordinate of the cell to place a fish in.
*/
public void addFish(int x, int y) {
if (cells[this.cellind(x,y)] == EMPTY) {
cells[this.cellind(x,y)] = FISH;
}
}
/**
* addShark() (with two parameters) places a newborn shark in cell (x, y) if
* the cell is empty. A "newborn" shark is equivalent to a shark that has
* just eaten. If the cell is already occupied, leave the cell as it is.
* @param x is the x-coordinate of the cell to place a shark in.
* @param y is the y-coordinate of the cell to place a shark in.
*/
public void addShark(int x, int y) {
int curpos = this.cellind(x,y);
if (cells[curpos] == EMPTY) {
cells[curpos] = SHARK;
hunger[curpos] = starvetime;
}
}
/**
* cellContents() returns EMPTY if cell (x, y) is empty, FISH if it contains
* a fish, and SHARK if it contains a shark.
* @param x is the x-coordinate of the cell whose contents are queried.
* @param y is the y-coordinate of the cell whose contents are queried.
*/
public int cellContents(int x, int y) {
return cells[this.cellind(x,y)]; // simply return the contents at the given index
}
/**
* timeStep() performs a simulation timestep as described in README.
* @return an ocean representing the elapse of one timestep.
* required actions:
* 1) If a cell contains a shark, and any of its neighbors is a fish, then the
* shark eats during the timestep, and it remains in the cell at the end of the
* timestep. (We may have multiple sharks sharing the same fish. This is fine;
* they all get enough to eat.)
*
* 2) If a cell contains a shark, and none of its neighbors is a fish, it gets
* hungrier during the timestep. If this timestep is the (starveTime + 1)th
* timestep the shark has gone through without eating, then the shark dies
* (disappears). Otherwise, it remains in the cell. An example demonstrating
* this rule appears below.
*
* 3) If a cell contains a fish, and all of its neighbors are either empty or are
* other fish, then the fish stays where it is.
*
* 4) If a cell contains a fish, and one of its neighbors is a shark, then the
* fish is eaten by a shark, and therefore disappears.
*
* 5) If a cell contains a fish, and two or more of its neighbors are sharks, then
* a new shark is born in that cell. Sharks are well-fed at birth; _after_ they
* are born, they can survive an additional starveTime timesteps without eating.
* (But they will die at the end of starveTime + 1 consecutive timesteps without
* eating.)
*
* 6) If a cell is empty, and fewer than two of its neighbors are fish, then the
* cell remains empty.
*
* 7) If a cell is empty, at least two of its neighbors are fish, and at most one
* of its neighbors is a shark, then a new fish is born in that cell.
*
* 8) If a cell is empty, at least two of its neighbors are fish, and at least two
* of its neighbors are sharks, then a new shark is born in that cell. (The new
* shark is well-fed at birth, even though it hasn't eaten a fish yet.)
*/
/** @return an array of neighbors around a given position **/
public int[] neighborarray(int pos) {
int[] array = new int[8];
int x = coordx(pos);
int y = coordy(pos);
array[0] = cellContents(x-1, y-1); // nw
array[1] = cellContents(x, y-1); // n
array[2] = cellContents(x+1, y-1); // ne
array[3] = cellContents(x+1, y); // e
array[4] = cellContents(x+1, y+1); // se
array[5] = cellContents(x, y+1); // s
array[6] = cellContents(x-1, y+1); // sw
array[7] = cellContents(x-1, y); // w
return array; }
/** @return the number of neighbors of a given type around a given position **/
public int neighbor(int type, int pos) {
int[] array = neighborarray(pos);
int number = 0;
for (int i=0; i<array.length; i++) {
if (array[i] == type) { number++; } }
return number; }
/** @return true if the method name's condition is satisfied around for a given position **/
public boolean caneat(int pos) { // 1 - If a cell contains a shark, and any of its neighbors is a fish
if (cells[pos] == SHARK && neighbor(FISH, pos)>0) {
return true;
} else { return false; } }
public boolean dangerous(int pos) { // 4 - If a cell contains a fish, and one of its neighbors is a shark
if (cells[pos] == FISH && neighbor(SHARK, pos)==1) {
return true;
} else { return false; } }
public boolean givesbirth(int pos) { /* 5 - If a cell contains a fish, and two or more of its neighbors are sharks
8 - If a cell is empty, at least two of its neighbors are fish, and at least two of its neighbors are sharks */
if (cells[pos] == FISH && neighbor(SHARK, pos)>1) {
return true;
} else if (cells[pos] == EMPTY && neighbor(FISH, pos)>1 && neighbor(SHARK, pos)>1) {
return true;
} else { return false; } }
public boolean spawnsfish(int pos) { // 7 - If a cell is empty, at least two of its neighbors are fish, and at most one of its neighbors is a shark
if (cells[pos] == EMPTY && neighbor(FISH, pos)>1 && neighbor(SHARK, pos)<2) {
return true;
} else { return false; } }
public Ocean timeStep() {
Ocean newocean = new Ocean(x, y, starvetime); // create new Ocean to hold the state after timeStep
/** Important notes: this new ocean is initially "blank". What this means here:
* If someone "dies" below, we don't need to do anything, because the cell in the new ocean is already EMPTY
* If any other values (i.e. hunger) change, they need to be written to the new ocean
* If the value of a given cell does not change, it MUST be copied to the new ocean
**/
for (int pos=0; pos<cells.length; pos++) {
if (caneat(pos)) { // the shark eats during the timestep, and it remains in the cell at the end of the timestep
newocean.cells[pos] = SHARK;
newocean.hunger[pos] = starvetime; }
else if (caneat(pos) != true && cells[pos]==SHARK) {
if (hunger[pos] == 0) { /* If this timestep is the (starveTime + 1)th timestep
the shark has gone through without eating
then the shark dies (disappears), so we do nothing since value is EMPTY by default */
} else { // otherwise decrease its turns to die by 1
newocean.cells[pos] = SHARK;
newocean.hunger[pos] = hunger[pos] - 1;
}
} else if (dangerous(pos)) { /* the fish is eaten by a shark and disappears, so do nothing */
} else if (givesbirth(pos)) { // a new shark is born in that cell; (sharks are well-fed at birth)
newocean.cells[pos] = SHARK;
newocean.hunger[pos] = starvetime;
} else if (spawnsfish(pos)) { newocean.cells[pos] = FISH; // a new fish is born in that cell
} else { newocean.cells[pos] = cells[pos]; } // in all other cases, just copy the existing value - CRUCIAL!
/** 3 - If a cell contains a fish, and all of its neighbors are either empty or are other fish, then the fish stays where it is.
if (pos.boring) { }
6 - If a cell is empty, and fewer than two of its neighbors are fish, then the cell remains empty.
if (pos.fishy) { }
**/
}
return newocean; // return the newly-created and modified ocean
}
/**
* The following method is required for Part II.
*/
/**
* addShark() (with three parameters) places a shark in cell (x, y) if the
* cell is empty. The shark's hunger is represented by the third parameter.
* If the cell is already occupied, leave the cell as it is. You will need
* this method to help convert run-length encodings to Oceans.
* @param x is the x-coordinate of the cell to place a shark in.
* @param y is the y-coordinate of the cell to place a shark in.
* @param feeding is an integer that indicates the shark's hunger. You may
* encode it any way you want; for instance, "feeding" may be the
* last timestep the shark was fed, or the amount of time that has
* passed since the shark was last fed, or the amount of time left
* before the shark will starve. It's up to you, but be consistent.
*/
public void addShark(int x, int y, int feeding) {
int curpos = this.cellind(x,y);
if (cells[curpos] == EMPTY) {
cells[curpos] = SHARK;
hunger[curpos] = feeding;
}
}
/**
* The following method is required for Part III.
*/
/**
* sharkFeeding() returns an integer that indicates the hunger of the shark
* in cell (x, y), using the same "feeding" representation as the parameter
* to addShark() described above. If cell (x, y) does not contain a shark,
* then its return value is undefined--that is, anything you want.
* Normally, this method should not be called if cell (x, y) does not
* contain a shark. You will need this method to help convert Oceans to
* run-length encodings.
* @param x is the x-coordinate of the cell whose contents are queried.
* @param y is the y-coordinate of the cell whose contents are queried.
*/
public int sharkFeeding(int x, int y) {
return hunger[this.cellind(x,y)];
}
/* The method below does the same thing as above, but takes an array position instead of (x,y) coords */
public int sharkFeeding(int pos) {
return sharkFeeding(coordx(pos), coordy(pos));
}
}
