universalSortingMechanism.sol

struct RandomizationMechanism {
  mapping(uint => uint) sortingMechanism;
  uint totalSorted;
  bytes32 entropy;
}
RandomizationMechanism sortingTool[];

function sortingHat(uint _sortingType, uint _listSize) internal returns (uint) {
  RandomizationMechanism storage s = sortingTool[_sortingType];
  s.totalSorted++;
  uint randomNumber = uint(sha3(block.blockhash(block.number-1), s.entropy, now)) % (_listSize - s.totalSorted);
  uint querySorter = s.totalSorted + randomNumber;
  // Instantiate sortingMechanism while people sort themselves
  if(s.sortingMechanism[querySorter] == 0) s.sortingMechanism[querySorter] = querySorter;
  if(sortingMechanism[totalSorted] == 0) s.sortingMechanism[s.totalSorted] = s.totalSorted;
  uint randomPosition = s.sortingMechanism[querySorter];
  s.sortingMechanism[randomPosition] = s.sortingMechanism[s.totalSorted];
  s.entropy = sha3(randomPosition, msg.sender, now);
  if(s.totalSorted == _listSize) s.totalSorted = 0;
  return randomPosition;
}