====== The Rubik's cube 2 by 2 ======
{{ :java:cubo_rubik_2x2.jpg?direct&100 |}}
Because I'm not good at all at solving this puzzle, I've decided to give Java an opportunity to solve it for me.
So, I've made a program to solve the rubik's cube. If you want to simply run the program, here it is:
{{:java:rubik.zip|}}
Just uncompress the contents of this zip file and you will find a file called ''rubik.jar''. Run it using the following command:
java -jar rubik.jar
And you the program will start.
Remember that the faces of the cube must be read as if you were reading a text: from left to right, topmost to bottom.
And the source code of the project:
{{:java:rubik_src.zip|}}
===== My comments =====
The data structure I've choose for the cube is in fact a 4x4 matrix of colors:
public class Cube22 implements Cube {
private static final int SIDE_SIZE = 2;
private static final String nl = System.getProperty("line.separator");
private Color[][][] cube = new Color[SIDE_SIZE+2][SIDE_SIZE+2][SIDE_SIZE+2];
// default constructor: a cube
// with all the colors correct
public Cube22()
{
/*
* TOP OF THE CUBE
* +-+-+-+-+
* | | | | |
* +-+-+-+-+
* | |b|b| |
* +-+-+-+-+
* | |b|b| |
* +-+-+-+-+
* | | | | |
* +-+-+-+-+
*/
cube[0][0][0] = Color.NOCOLOR; cube[1][0][0] = Color.NOCOLOR; cube[2][0][0] = Color.NOCOLOR; cube[3][0][0] = Color.NOCOLOR;
cube[0][1][0] = Color.NOCOLOR; cube[1][1][0] = Color.BLUE; cube[2][1][0] = Color.BLUE; cube[3][1][0] = Color.NOCOLOR;
cube[0][2][0] = Color.NOCOLOR; cube[1][2][0] = Color.BLUE; cube[2][2][0] = Color.BLUE; cube[3][2][0] = Color.NOCOLOR;
cube[0][3][0] = Color.NOCOLOR; cube[1][3][0] = Color.NOCOLOR; cube[2][3][0] = Color.NOCOLOR; cube[3][3][0] = Color.NOCOLOR;
/*
* VERTICAL COLORS, 1
* +-+-+-+-+
* | |V|V| |
* +-+-+-+-+
* |W| | |Y|
* +-+-+-+-+
* |W| | |Y|
* +-+-+-+-+
* | |R|R| |
* +-+-+-+-+
*/
cube[0][0][1] = Color.NOCOLOR; cube[1][0][1] = Color.VIOLET; cube[2][0][1] = Color.VIOLET; cube[3][0][1] = Color.NOCOLOR;
cube[0][1][1] = Color.WHITE; cube[1][1][1] = Color.NOCOLOR; cube[2][1][1] = Color.NOCOLOR; cube[3][1][1] = Color.YELLOW;
cube[0][2][1] = Color.WHITE; cube[1][2][1] = Color.NOCOLOR; cube[2][2][1] = Color.NOCOLOR; cube[3][2][1] = Color.YELLOW;
cube[0][3][1] = Color.NOCOLOR; cube[1][3][1] = Color.RED; cube[2][3][1] = Color.RED; cube[3][3][1] = Color.NOCOLOR;
/*
* VERTICAL COLORS, 2
* +-+-+-+-+
* | |V|V| |
* +-+-+-+-+
* |W| | |Y|
* +-+-+-+-+
* |W| | |Y|
* +-+-+-+-+
* | |R|R| |
* +-+-+-+-+
*/
cube[0][0][2] = Color.NOCOLOR; cube[1][0][2] = Color.VIOLET; cube[2][0][2] = Color.VIOLET; cube[3][0][2] = Color.NOCOLOR;
cube[0][1][2] = Color.WHITE; cube[1][1][2] = Color.NOCOLOR; cube[2][1][2] = Color.NOCOLOR; cube[3][1][2] = Color.YELLOW;
cube[0][2][2] = Color.WHITE; cube[1][2][2] = Color.NOCOLOR; cube[2][2][2] = Color.NOCOLOR; cube[3][2][2] = Color.YELLOW;
cube[0][3][2] = Color.NOCOLOR; cube[1][3][2] = Color.RED; cube[2][3][2] = Color.RED; cube[3][3][2] = Color.NOCOLOR;
/*
* BOTTOM OF THE CUBE
* +-+-+-+-+
* | | | | |
* +-+-+-+-+
* | |G|G| |
* +-+-+-+-+
* | |G|G| |
* +-+-+-+-+
* | | | | |
* +-+-+-+-+
*/
cube[0][0][3] = Color.NOCOLOR; cube[1][0][3] = Color.NOCOLOR; cube[2][0][3] = Color.NOCOLOR; cube[3][0][3] = Color.NOCOLOR;
cube[0][1][3] = Color.NOCOLOR; cube[1][1][3] = Color.GREEN; cube[2][1][3] = Color.GREEN; cube[3][1][3] = Color.NOCOLOR;
cube[0][2][3] = Color.NOCOLOR; cube[1][2][3] = Color.GREEN; cube[2][2][3] = Color.GREEN; cube[3][2][3] = Color.NOCOLOR;
cube[0][3][3] = Color.NOCOLOR; cube[1][3][3] = Color.NOCOLOR; cube[2][3][3] = Color.NOCOLOR; cube[3][3][3] = Color.NOCOLOR;
} // Cube22
@Override
public Color getColor( int x, int y, int z )
{
return cube[x][y][z];
}
@Override
public void setColor( int x, int y, int z, Color color )
{
cube[x][y][z] = color;
}
@Override
public Cube getCopy()
{
Cube22 result = new Cube22();
for( int x = 0; x < 4; x++ )
for( int y = 0; y < 4; y++ )
for( int z = 0; z < 4; z++ )
{
result.setColor(x, y, z, getColor(x, y, z));
}
return result;
} // getCopy
@Override
public String toString()
{
StringBuilder out = new StringBuilder();
out.append( " ____________ " ); out.append( nl );
out.append( " / / /|" ); out.append( nl );
out.append( " / "+Color.toString(cube[1][1][0])+" / "+Color.toString(cube[2][1][0])+" / |" ); out.append( nl );
out.append( " /_____/_____/ "+Color.toString(cube[3][1][1])+"|" ); out.append( nl );
out.append( " / / /| ," ); out.append( nl );
out.append( " / "+Color.toString(cube[1][2][0])+" / "+Color.toString(cube[2][2][0])+" / | /|" ); out.append( nl );
out.append( " /_____/_____/ |/ |" ); out.append( nl );
out.append( " | | |"+Color.toString(cube[3][2][1])+" / "+Color.toString(cube[3][1][2])+"," ); out.append( nl );
out.append( " | "+Color.toString(cube[1][3][1])+" | "+Color.toString(cube[2][3][1])+" | /| / " ); out.append( nl );
out.append( " |_____|_____|/ |/ " ); out.append( nl );
out.append( " | | |"+Color.toString(cube[3][2][2])+" / " ); out.append( nl );
out.append( " | "+Color.toString(cube[1][3][2])+" | "+Color.toString(cube[2][3][2])+" | / " ); out.append( nl );
out.append( " |_____|_____|/ " ); out.append( nl );
return out.toString();
} // toString
/**
* Return true if the cube is solved, in other words, all the colors
* are grouped in the same face of the cube.
*
* @return
*/
@Override
public boolean isSolved()
{
boolean facade1;
boolean facade2;
boolean facade3;
boolean facade4;
boolean facade5;
boolean facade6;
facade1 = cube[1][1][0] == cube[2][1][0] && cube[2][1][0] == cube[1][2][0] && cube[1][2][0] == cube[2][2][0];
facade2 = cube[3][2][1] == cube[3][1][1] && cube[3][1][1] == cube[3][1][2] && cube[3][1][2] == cube[3][2][2];
facade3 = cube[1][3][1] == cube[2][3][1] && cube[2][3][1] == cube[1][3][2] && cube[1][3][2] == cube[2][3][2];
facade4 = cube[1][1][3] == cube[2][1][3] && cube[2][1][3] == cube[1][2][3] && cube[1][2][3] == cube[2][2][3];
facade5 = cube[0][2][1] == cube[0][1][1] && cube[0][1][1] == cube[0][1][2] && cube[0][1][2] == cube[0][2][2];
facade6 = cube[1][0][1] == cube[2][0][1] && cube[2][0][1] == cube[1][0][2] && cube[1][0][2] == cube[2][0][2];
return facade1 && facade2 && facade3 && facade4 && facade5 && facade6;
}
/**
* Determine if two cubes are equal regardless of their orientation.
* This is important because this, applied to the search algorithm
* prevents to explore branches that in fact are the seame than a
* previous one but with the colors rotated.
*
*/
@Override
public boolean equals( Object comp )
{
if( this == comp )
return true;
if( comp instanceof Cube22 )
{
Cube22 compCube = (Cube22) comp;
return equalsXYZ(compCube);
}
else
return false;
} // equals
public boolean equalsXYZ( Cube compCube )
{
boolean equal = true;
for( int x = 0; x < SIDE_SIZE+2 && equal; x++ )
for( int y = 0; y < SIDE_SIZE+2 && equal; y++ )
for( int z = 0; z < SIDE_SIZE+2 && equal; z++ )
equal = equal && (cube[x][y][z] == compCube.getColor(x, y, z));
return equal;
} // equals
}
After two days developing (in my spare time) I've realized that it was a wrong decision, because there is a better way to store the cube and allow the rotation operations to be more easy: is to create a ''sticker'' data structure and link the stickers between them. Thus, the operation of rotation of the cube is more easy and less error prone.
An idea of what it would be:
class Sticker
{
private Sticker north;
private Sticker south;
private Sticker east;
private Sticker west;
private Sticker northCorner;
}
So, the cube is constructer by linking the respective north, south, east ... links between them. But I think it would be needed to keep a link in order to know the orientation of the cube (to know what is ''up'' and ''down''): because of this is necessary this ''northCorner'', who will be set with a value only with one sticker.