Alguns meses atrás participei do Boot Camp da Thoughworks (
empresa do Martin Fowler - um dos criadores da UML) e hoje resolvi repassar o código fonte que desenvolvi. O problema foi dado em uma folha em ingles para a interpretação e solução em formato XP (Extreme Programming) que é feito em duplas, porém o código não poderia ser o mesmo para os participantes. O problema é um Mars Rovers, um robô com movimentação remota que poderia ser utilizado em Marte. Tive a sorte de encontrar um ex-colega de faculdade, Tato Dutra e rápidamente encontramos a solução composta por direção e movimento. Consegui finalizar o código antes do restante e enquanto o Tato pensou em uma função para as Direções Norte, Sul, Leste e Oeste eu criei uma tabela para utilizar como função no programa. Segue o problema, a solução e os códigos. Era obrigatório o uso de OO.
Problem One: Mars Rovers
A squad of robotic rovers are to be by NASA on a plateau on Mars. This plateau, which is curiously rectangular, must be navigated by the rovers so that their on-board cameras can get a complete view of the surrounding terrain to send back to Earth.
A rover's position and location is representted by a combination of x and y co-ordinates and a letter representing one of the four cardinal compass points. The plateau is divided up into a grid to simplify navigation. An example position might be 0, 0, M which means the rover is in the botton left corner and facing North.
In order to control a cover, NASA sends a simple string of letters. The possible letters are "L", "R" and "M". "L" and "R" makes de rover spin 90 degrees left or right respectively, without moving from its current spot. "M" means move forward one grid point, and maintain the same heading.
Assume that the square directly North from (x, y) is (x, y+1).
INPUT: The first line of inputs is the upper-right coordinates of the plateau, the lower-left coordinates are assumed to be 0, 0.
The rest of the input is information pertaining to the rovers that have been deployed. Each rover has two lines of input. The first line gives the rover's position, and the second line is a series of instructions telling the rover how to explore the plateau.
The position is made up of two integers and a letter separated by spaces, corresponding to the x and y co-ordinates and the rover's orientation.
Each rover will be finished sequentially, which means that the second rover won't start to move until the first one has finished moving.
OUTPUT The output for each rover should be its final co-ordinates and heading.
INPUT AND OUTPUT
Test Input: 5 5 1 2 N LMLMLMLMM 3 3 E MMRMMRMRRM
Expected Output: 1 3 N 5 1 E
Dificil foi descobrir o que eram as entradas e o que significava cada letra, assim como descobrir o que era a saída, até porque o tempo era curto. Mas chegamos à solução:
Tabela do Tato (Sobre eixos X e Y):
N = X, Y+1
S = X, Y-1
E = X+1,Y
W = X-1, Y
Tabela Boá (Aplicação do Movimento Left Right)
Face - Left - Right
N - W - E
S - E - W
E - N - S
W - S - N
Criei três pacotes view, operation e objects com os arquivos dentro:
view/TestCoord.java (main)
operation/NewFront.java
operation/NewPosition.java
objects/Instruction.java
objects/Position.java
view/TestCoord.java
package view;
import javax.swing.JOptionPane;
import objects.Position;
import operation.NewFront;
import operation.NewPosition;
public class TestCoord {
/**
* @AUTOR MARCELO BOÁ
* @
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
NewFront newFront = new NewFront();
NewPosition newPosition = new NewPosition();
String coordinate = null;
String instruction = null;
int posX=0;
int posY=2;
int posFace=4;
String myFace;
String myPosX;
String myPosY;
char[] coordinateChars;
char[] instructionChars;
coordinate = JOptionPane.showInputDialog("Enter "
+ "with the last position coordinate!Format[X Y Face]");
instruction = JOptionPane.showInputDialog("Enter "
+ "with the last position coordinate!Format[LMLMRMM]");
Position position = new Position();
String[] coordinateStrings = coordinate.split(" ");
coordinateChars = coordinate.toCharArray();
instructionChars = instruction.toCharArray();
myPosX=coordinateStrings[0];
myPosY=coordinateStrings[1];
myFace=coordinateStrings[2];
position.setCoordX(Integer.parseInt(myPosX));
position.setCoordY(Integer.parseInt(myPosY));
char ch = myFace.charAt (0);
position.setFace(ch);
System.out.println(position.getCoordX());
System.out.println(position.getCoordY());
System.out.println(position.getFace());
for (int i = 0; i < instructionChars.length; i++) {
System.out.println(instructionChars[i]);
position=newFront.getNewFront(position, instructionChars[i]);
}
System.out.println(position.getCoordX());
System.out.println(position.getCoordY());
System.out.println(position.getFace());
JOptionPane.showMessageDialog(null, position.getCoordX()+" "
+position.getCoordY()+" "+position.getFace());
}
}
operation/NewFront.java
package operation;
import objects.Position;
import operation.NewPosition;;
public class NewFront {
NewPosition position = new NewPosition();
public Position getNewFront(Position pos, char singleInstruction) {
char singlePos = pos.getFace();
if (singleInstruction != 'M') {
if (singleInstruction == 'L') {
switch ( singlePos ) {
case 'N':
pos.setFace('W');
break;
case 'S':
pos.setFace('E');
break;
case 'E':
pos.setFace('N');
break;
case 'W':
pos.setFace('S');
break;
}
} else {// singleInstruction=='L'
if(singleInstruction=='R'){
switch( singlePos ) {
case 'N':
pos.setFace('E');
break;
case 'S':
pos.setFace('W');
break;
case 'E':
pos.setFace('S');
break;
case 'W':
pos.setFace('N');
break;
}
}
}
} else {// singleInstruction=='R'
pos=position.getNewPos(pos, singleInstruction);
}
return pos;
}
public NewFront() {
super();
// TODO Auto-generated constructor stub
}
}
operation/NewPosition.java
package operation;
import objects.Position;
public class NewPosition {
public Position getNewPos(Position pos, char singleInstruction) {
char face = pos.getFace();
int coordX=pos.getCoordX();
int coordY=pos.getCoordY();
switch ( face ) {
case 'N':
coordY++;
pos.setCoordY(coordY);
break;
case 'S':
coordY--;
pos.setCoordY(coordY);
break;
case 'E':
coordX++;
pos.setCoordX(coordX);
break;
case 'W':
coordX--;
pos.setCoordX(coordX);
break;
}
return pos;
}
public NewPosition() {
super();
// TODO Auto-generated constructor stub
}
}
objects/Instruction.java
package objects;
public class Instruction {
private String instruction;
public Instruction() {
super();
// TODO Auto-generated constructor stub
}
public String getInstruction() {
return instruction;
}
public void setInstruction(String instruction) {
this.instruction = instruction;
}
}
objects/Position.java
package objects;
public class Position {
private int coordX;
private int coordY;
private char face;
public Position() {
super();
// TODO Auto-generated constructor stub
}
public Position(int coordX, int coordY, char face) {
super();
this.coordX = coordX;
this.coordY = coordY;
this.face = face;
}
public int getCoordX() {
return coordX;
}
public void setCoordX(int coordX) {
this.coordX = coordX;
}
public int getCoordY() {
return coordY;
}
public void setCoordY(int coordY) {
this.coordY = coordY;
}
public char getFace() {
return face;
}
public void setFace(char face) {
this.face = face;
}
}
Participar de um Boot Camp foi experiência fora de série!
