Magic Cube

// Solved 3x3x3 Cube maps to "UUUUUUUUURRRRRRRRRFFFFFFFFFDDDDDDDDDLLLLLLLLLBBBBBBBBB"

// s : size of the cube; let index = a*s + b    (i.e. a,b = row,column)

//

// Up    :   index --> b<s-1 ? (s-1)*(s+4b)+a : 6*s*s -13*s +8 +a

// Front :   index --> if b==0  : s*s - 1 - index

//                     if b==s-1: 6*s*s -11*s +6 - index

//                     else

//                         a==0: s*s + s-1 + 4*(b-1)*(s-1) + 2*(s-2) + s

//                         else: s*s + s-1 + 4*(b-1)*(s-1) + 2*(s-1-a)

// Down  :   index --> b==0 ? (s-1-a) : s*s + s-1 + 4*(b-1)*(s-1) - a

// Left  :   index --> (s-1-a)*s + b

// Back  :   index --> if b==s-1: s*(s-1-a)

//                     if b==0  : 5*s*s -12*s + 8 + (s-1-a)*s

//                     else

//                        if a==s-1: s*s + 4*(s-2-b)*(s-1)

//                        else     : s*s + 4*(s-2-b)*(s-1) + s + (s-2-a)*2

    StringBuilder objectString = new StringBuilder();

    int size = getSize();

    int len = size*size;

    int cubitIndex, row, col;

    int color;

    final int RIGHT= 0;

    final int LEFT = 1;

    final int UP   = 2;

    final int DOWN = 3;

    final int FRONT= 4;

    final int BACK = 5;

    final char[] FACE_NAMES = { 'R', 'L', 'U', 'D', 'F', 'B'};

    for(int i=0; i<len; i++)

      {

      row = i/size;

      col = i%size;

      cubitIndex = col<size-1 ? (size-1)*(size+4*col) + row : 6*size*size - 13*size + 8 + row;

      color = getCubitFaceColorIndex(cubitIndex,UP);

      objectString.append(FACE_NAMES[color]);

      }

    for(int i=0; i<len; i++)

      {

      cubitIndex = 6*size*size - 12*size +7 - i;

      color = getCubitFaceColorIndex(cubitIndex,RIGHT);

      objectString.append(FACE_NAMES[color]);

      }

    for(int i=0; i<len; i++)

      {

      row = i/size;

      col = i%size;

      if( col==size-1 ) cubitIndex = 6*size*size - 11*size + 6 -i;

      else if( col==0 ) cubitIndex = size*size - 1 - i;

      else

        {

        if( row==0 ) cubitIndex = size*size + size-1 + 4*(col-1)*(size-1) + 2*(size-2) + size;

        else         cubitIndex = size*size + size-1 + 4*(col-1)*(size-1) + 2*(size-1-row);

        }

      color = getCubitFaceColorIndex(cubitIndex,FRONT);

      objectString.append(FACE_NAMES[color]);

      }

    for(int i=0; i<len; i++)

      {

      row = i/size;

      col = i%size;

      cubitIndex = col==0 ? size-1-row : size*size + size-1 + 4*(col-1)*(size-1) - row;

      color = getCubitFaceColorIndex(cubitIndex,DOWN);

      objectString.append(FACE_NAMES[color]);

      }

    for(int i=0; i<len; i++)

      {

      row = i/size;

      col = i%size;

      cubitIndex = (size-1-row)*size + col;

      color = getCubitFaceColorIndex(cubitIndex,LEFT);

      objectString.append(FACE_NAMES[color]);

      }

    for(int i=0; i<len; i++)

      {

      row = i/size;

      col = i%size;

      if( col==size-1 ) cubitIndex = size*(size-1-row);

      else if( col==0 ) cubitIndex = 5*size*size - 12*size + 8 + (size-1-row)*size;

      else

        {

        if( row==size-1 ) cubitIndex = size*size + 4*(size-2-col)*(size-1);

        else              cubitIndex = size*size + 4*(size-2-col)*(size-1) + size + 2*(size-2-row);

        }

      color = getCubitFaceColorIndex(cubitIndex,BACK);

      objectString.append(FACE_NAMES[color]);

      }

    // android.util.Log.e("cube", "string: "+objectString.toString());

    return objectString.toString();

///////////////////////////////////////////////////////////////////////////////////////////////////

  int getCubitFaceColorIndex(int cubit, int face)

    {

    return mCubits[cubit].getColorIndex(face);

    }