Target Sum - return all sets [using Lists]

program Project1;
{$APPTYPE CONSOLE}
uses
  System.SysUtils, Generics.Collections;
//
//  Generate a list of all sub-lists that sum to the target figure.
//
//  Nice reference :  https://stackoverflow.com/questions/9315275/dynamic-tlist-of-tlist

function target_sum(const a : TList<integer>; const k,x : integer) : TObjectlist< TList<integer> >;
begin
  if k = a.Count then begin
                        result := TObjectlist< TList<integer> >.create;     //  []
                        exit;
                      end;

  if x = a[k]    then begin
                        var single := TList<integer>.Create;                //  []
                        single.add( a[k] );                                 //  [ a[k] ]
                        result    := TObjectlist< TList<integer> >.create;
                        result.add(single);                                 //  [ [a[k]] ]
                        exit;
                      end
  else
                      begin
                        var s := target_sum(a, k + 1, x       );            // not using a[k]
                        var t := target_sum(a, k + 1, x - a[k]);            //     using a[k]
                        if t.count > 0 then
                             for var list in t do begin
                                 list.Insert(0, a[k]);
                                 s.add( list );
                             end
                        else t.free;
                        result := s;
                      end;
end;


procedure print_list(const list : TList<integer>);
begin
  for var i in list do write(i, ', ');  writeln;
end;


var
  a : TList<integer>;
  s : TObjectlist< TList<integer> >;
const
  target = 0;

begin
  ReportMemoryLeaksOnShutdown := true;                              //  leaking objects

  a := TList<integer>.Create;
  a.AddRange([1, 4, 5, 2, 7, 8, -3, -5, -6, 9, 3, -7, -1, 5, 6]);   // result = 436
  //a.addrange([1,2,-1,-2]);    // result = 3

  s := target_sum(a,0,target);
  write('Target = ', target, ' from : '); print_list(a);  writeln;

  writeln('# Solutions = ', s.count); writeln;

  if s.Count > 0 then for var list in s do print_list(list)
                 else writeln('x');

  s.free;
  a.free;
  readln;
end.


(*  Javascript

function target_sum(a, k, x) {
    if (k == a.length) return [];
    if (a[k] == x) {
        return [ [a[k]] ];
    } else {
        var s = target_sum(a, k + 1, x); // not using a[k]
        var t = target_sum(a, k + 1, x - a[k]); // using a[k]
        for (var i = 0; i < t.length; ++i) {
            t[i].unshift(a[k]); // a[k] is part of the solution
            s.push(t[i]); // merge t[] into s[]
        }
        return s;
    }
}

var s = target_sum([1, 4, 5, 2, 7, 8, -3, -5, -6, 9, 3, -7, -1, 5, 6], 0, 0);
for (var i = 0; i < s.length; ++i)
    console.log(s[i].join(","));

*)