How would you represent a Rubik's Cube in code?

Question

If you were developing software to solve a Rubik\'s Cube, how would you represent the cube?

Answer 1

The shortest representation is something like this one: codepen.io/Omelyan/pen/BKmedK

The cube is unwrapped in 1D array (vector of 54 elements). A few-line rotation function swaps stickers and based on the cube's symmetry. Here's complete working model in C, I made it in 2007 when was a student:

const byte // symmetry
  M[] = {2,4,3,5},
  I[] = {2,0,4,6};

byte cube[55]; // 0,0,0,0,0,0,0,0,0, 1,1,1,1,1,1,1,1,1, ... need to be filled first

#define m9(f, m) (m6(f, m)*9)

byte m6(byte f, byte m) {return ((f&~1)+M[m+(f&1)*(3-2*m)])%6;}

void swap(byte a, byte b, byte n) {
  while (n--) {byte t=cube[a+n]; cube[a+n]=cube[b+n]; cube[b+n]=t;}
}

void rotate(byte f, byte a) { // where f is face, and a is number of 90 degree turns
  int c=m9(f, 3), i;
  swap(c, c+8, 1);
  while (a--%4) for (i=2; i>=0; --i)
    swap(m9(f, i) + I[i], m9(f, i+1) + I[i+1], 3),
    swap(f*9+i*2, f*9+i*2+2, 2);
  swap(c, c+8, 1);
}