How to insert character in all possible positions of a string? - delphi

Question

I want to insert a char into every possible position of s string except start and end.
e.g.
abc
I want to have
a-bc
ab-c
a-b-c
Below is my test, but not correct:
procedure TForm1.Button2Click(Sender: TObject);
var
start, i,j,k,position,loop: integer;
laststart,lastend:integer;
c,item,stem:string;
str, prefix:string;
begin
str:='abcd';
memo1.clear;
memo1.Lines.Add(str);
laststart:=0;
lastend:=memo1.lines.count-1;
position:=0;
prefix:='';
loop:=0;
while loop<=length(str)-1 do
begin
for j:= laststart to lastend do
begin
item:=memo1.lines[j];
for k:=length(item) downto 1 do
begin
if item[k]='-' then
begin
position:=j;
break;
end;
end; //for k
prefix:=copy(item,1,position);
stem:=copy(item,position+1, length(item));
for start:=1 to length(stem)-1 do
begin
c:=prefix+copy(stem,1,start)+'-'+
copy(stem, start+1,length(stem));
memo1.lines.add(c);
end;
end; //for j
laststart:=lastend+1;
lastend:=memo1.Lines.Count-1;
inc(loop);
end; //end while
end;
it outputs:
abcd
a-bcd
ab-cd
abc-d
a--bcd // not correct
a-b-cd
a-bc-d
ab--cd //incorrect
ab-c-d
abc--d //incorrect
a--bc-d //incorrect
I feel the maximum possible breaks is lenth(str)-1, abc->most possible is insert 2 '-' (twice). Is this correct?
And are there other faster ways to do it?
Thanks a lot.

Answer 1

Recursive version.
procedure InsertSymbols(s: string; c: Char; Position: Integer = 1);
var
i: Integer;
begin
Memo1.Lines.Add(s);
for i := Position to Length(s) - 1 do
InsertSymbols(Copy(s, 1, i) + c + Copy(s, i + 1, Length(s) - i), c, i + 2);
end;
begin
InsertSymbols('Test', '-');
end;

Answer 2

This works:
procedure TForm4.Button1Click(Sender: TObject);
var
S: string;
N: integer;
Marker: cardinal;
MaxMarker: cardinal;
Str: string;
i: Integer;
begin
S := Edit1.Text;
N := length(S);
Marker := 0;
MaxMarker := 1 shl (N - 1) - 1;
Memo1.Clear;
Memo1.Lines.BeginUpdate;
for Marker := 0 to MaxMarker do
begin
Str := S[1];
for i := 2 to N do
begin
if (Marker shr (N-i)) and 1 <> 0 then
Str := Str + '-';
Str := Str + S[i];
end;
Memo1.Lines.Add(Str);
end;
Memo1.Lines.EndUpdate;
end;
As you can see, it works by using binary representation of numbers:
t e s t
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1

Answer 3

Why all the difficult solutions?
Just copy the string to a new one char by char, add hyphens in between, except for the last one.

Answer 4

I needed to separate a string to use as a serial number and here is the code:
Function GetDashedKey(Key: string): string
const
PartSize = 7;
var
Indx: Integer;
dashedKey : string;
begin
repeat
if Trim(dashedKey)<>'' then
dashedKey := dashedKey + ' - ';
if Length(Key) < PartSize then
begin
dashedKey := dashedKey + Key;
Key := '';
end
else
begin
dashedKey := dashedKey + Copy(Key, 1, PartSize);
Key := Copy(Key, PartSize + 1, Length(Key)-1);
end;
until Trim(Key) = '';
Result := dashedKey;
end;