Magic Cube

  private int retFreeCornerPermutation(int[] perm, int[][] corners)

    perm[0] = -1;

    perm[3] = -1;

      int[] cor = corners[map[i]];

      if( cornerIs(cor,2,5,0) ) perm[0] = i;

      if( cornerIs(cor,3,4,0) ) perm[1] = i;

      if( cornerIs(cor,1,2,4) ) perm[2] = i;

      if( cornerIs(cor,1,3,5) ) perm[3] = i;

    if( perm[0]==-1 ) return ERROR_CORNER_025_MISSING;

    if( perm[1]==-1 ) return ERROR_CORNER_034_MISSING;

    if( perm[2]==-1 ) return ERROR_CORNER_124_MISSING;

    if( perm[3]==-1 ) return ERROR_CORNER_135_MISSING;

  // [1][] are the 3 quats the 1st 'fixed' corner will have when 'fakeTwisted' (which in case of

  // the fixed corners is the same as the final twist) with respectively twist 0,1,2.

  private final int[][] fixedQuats = { {0,1,2},{0,7,8},{0,6,5},{0,4,3} };

  // [1][2][] are the 3 quats the 1st free corner, when permuted to the location of the 2nd corner,

  // will have when it is 'fakeTwisted' with fakeTwist 0,1,2.

  // fakeTwist is an intermediate twist which needs yet to be translated to the final twist of the

  // corners (which needs to sum up to something divisible by 3).

  private final int[][][] freeQuats=

    {

        { {0,3,4},{9,8,1},{6,11,2},{7,10,5} },

        { {9,2,7},{0,5,6},{1,10,3},{4,11,8} },

        { {5,1,11},{2,4,10},{0,8,7},{9,3,6} },

        { {8,6,10},{3,7,11},{9,5,4},{0,2,1} }

    };

  private void fillInQuats(int[] output, int[] perm, int[] twist)

    {

    output[0] = fixedQuats[0][twist[0]];

    output[1] = freeQuats[0][perm[0]][twist[1]];

    output[2] = freeQuats[1][perm[1]][twist[2]];

    output[3] = fixedQuats[1][twist[3]];

    output[4] = freeQuats[2][perm[2]][twist[3]];

    output[5] = fixedQuats[2][twist[5]];

    output[6] = fixedQuats[3][twist[6]];

    output[7] = freeQuats[3][perm[3]][twist[7]];

  private int computeLocation(int quat)

    for(int i=0; i<4; i++)

      int[] q = freeQuats[0][i];

      if( quat==q[0] || quat==q[1] || quat==q[2] ) return i;

    android.util.Log.e("D", "error in computeLocation, quat="+quat);

    return -1;

    }

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

  private int retFixed(int index, int quat)

    {

    int[] qs = fixedQuats[index];

    if( quat==qs[0]) return 0;

    if( quat==qs[1]) return 1;

    if( quat==qs[2]) return 2;

    android.util.Log.e("D", "error in retFixed, index="+index+" quat="+quat);

    return -1;

    }

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

  private int retFree(int index, int quat)

    {

    int[][] qs = freeQuats[index];

    for(int i=0; i<4; i++)

      if( quat==qs[i][0]) return 0;

      if( quat==qs[i][1]) return 1;

      if( quat==qs[i][2]) return 2;

    android.util.Log.e("D", "error in retFree, index="+index+" quat="+quat);

    return -1;

// In case of the four 'fixed' corners (0,3,5,6) which do not change their location,

// the twist is natural: 0 in the init positions and increasing 1 mod 3 on each CW turn.

//

// In case of the four 'free' corners their twist is relative to the position of the 'free'

// tetrahedron. And so, for example the twist of free corner 1 (whose 0th face is orange) is equal

// to 0 if free corner 7 is on the same face like 0th face of corner 1 (which is the case in init

// position); then once free corners 2,4,7 permute CW, twist of corner 1 increases by 1 mod 3.

  private void computeCornerTwists(int[] twists, int[] quats)

    twists[0] = retFixed(0,quats[0]);

    twists[3] = retFixed(1,quats[3]);

    twists[5] = retFixed(2,quats[5]);

    twists[6] = retFixed(3,quats[6]);

    twists[1] = retFree(0,quats[1]);

    twists[2] = retFree(1,quats[2]);

    twists[4] = retFree(2,quats[4]);

    twists[7] = retFree(3,quats[7]);

    }

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

  private int retCornerPerm(int index, int[] perm)

    {

    int[] free = {1,2,4,7};

    switch(index)

      {

      case 0: return 0;

      case 1: return free[perm[0]];

      case 2: return free[perm[1]];

      case 3: return 3;

      case 4: return free[perm[2]];

      case 5: return 5;

      case 6: return 6;

      case 7: return free[perm[3]];

      }

    return -1;

    }

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

  private void computeCornerQuats(int[] quats, int[][] corners, int[] perm)

    {

    final int[] map = { 4,2,3,5,1,5,4,1 };

    int[] twists = new int[8];

    for(int i=0; i<8; i++)

      int color = mFaceColors[map[i]];

      int[] c = corners[retCornerPerm(i,perm)];

           if( c[0]==color ) twists[i] = 0;

      else if( c[1]==color ) twists[i] = 1;

      else                   twists[i] = 2;

    fillInQuats(quats,perm,twists);

    int[] freePerm = new int[4];

    int[] quats    = new int[8];

    int result4 = retFreeCornerPermutation(freePerm,corners);

    computeCornerQuats(quats,corners,freePerm);

    computeCornerTwists(twist,quats);

/*

for(int i=0; i<4; i++) android.util.Log.e("D", "perm "+i+" : "+freePerm[i]);

for(int i=0; i<8; i++) android.util.Log.e("D", "quat "+i+" : "+quats[i]);

*/

    int total = twist[1]+twist[2]+twist[4]+twist[7];

    if( (total%3)!=0 ) return ERROR_CORNER_TWISTED;

    int totalTwist = twist[0]+ 3*(twist[1]+ 3*(twist[2]+ 3*(twist[3]+ 3*(twist[4]+ 3*(twist[5]+ 3*twist[6])))));

    int locationOfFree0 = computeLocation(quats[1]);

    return center_perm_num+ 360*(totalTwist + 2187*locationOfFree0);