德尔福阵列的电源组

type
  TIdArray = array of Integer;
  TPowerSet = array of TIdArray;

function PowerSet(Ids: TIdArray): TPowerSet;
// Implementation loosely based on the explanation on
// http://www.mathsisfun.com/sets/power-set.html
var
  @R_388_10586@lCombinations: Integer;
  @R_388_10586@lItems: Integer;
  Combination: Integer;
  sourceItem: Integer;
  ResultItem: Integer;
  Bit,Bits: Integer;
begin
  @R_388_10586@lItems := Length(Ids);

  // @R_388_10586@l number of combination for array of n items = 2 ^ n.
  @R_388_10586@lCombinations := 1 shl @R_388_10586@lItems;

  SetLength(Result,@R_388_10586@lCombinations);

  for Combination := 0 to @R_388_10586@lCombinations - 1 do
  begin
    // The Combination variable contains a bitmask that tells us which items
    // to take from the array to construct the current combination.
    // Disadvantage is that because of this method,the input array may contain
    // at most 32 items.

    // Count the number of bits set in Combination. This is the number of items
    // we need to allocate for this combination.
    Bits := 0;
    for Bit := 0 to @R_388_10586@lItems - 1 do
      if Combination and (1 shl Bit) <> 0 then
        Inc(Bits);

    // Allocate the items.
    SetLength(result[Combination],Bits);

    // Copy the right items to the current result item.
    ResultItem := 0;

    for sourceItem := 0 to @R_388_10586@lItems - 1 do
      if Combination and (1 shl sourceItem) <> 0 then
      begin
        result[Combination][ResultItem] := Ids[sourceItem];
        Inc(ResultItem);
      end;
  end;

end;