Get an array of the bit positions within a 64-bit integer

Question

OK, it may sound a bit complicated, but this is what I\'m trying to do :

• Take e.g. 10101010101
• And return { 0, 2, 4, 6, 8, 10 }

Answer 1

const size_t size = sizeof(U64)*8;
U64 val = 1;

vector res;
res.reserve(size);

for ( size_t i = size; i > 0; --i ) {
  if ( ( val & bitboard ) != 0 ) {
    res.push_back(i);
  }
  val <<= 1;
}