反转字符串

function ReverseString1(const s: string): string;
var
i, len: Integer;
begin
len := Length(s);
SetLength(Result, len);
for i := len downto 1 do
begin
Result[len - i + 1] := s;
end;
end;
function ReverseString2(const Str: string): string;
// by Ido Kanner
var
ch: Char;
i, Size: Integer;
begin
Result := Str;
Size := Length(Result);
if (Size >= 2) then
// 2 or more chars
begin
// For 1 to middle of the string
for i := 1 to (Size div 2) do
begin
// Lets get the charecter of the current place in the string
ch := Result;
// Place the Current pos of the char
// with the char of it's mirror place...
Result := Result[Size - (i - 1)];
// In the mirror place we will put char of the
// Original place... And we switched places !!!
Result[Size - (i - 1)] := ch;
end
end;
end;
　
function ReverseString3(S: string): string;
// by Rudy Velthuis
var
P, Q: PChar;
C: Char;
begin
Result := S;
if Length(Result) = 0 then Exit;
P := PChar(Result);
Q := P + Length(Result) - 1;
while P < Q do
begin
C := P^;
P^ := Q^;
Q^ := C;
Inc(P);
Dec(Q);
end;
end;
procedure ReverseString4(var S: string);
// by Rudy Velthuis
var
P, Q: PChar;
C: Char;
begin
if Length(S) = 0 then Exit;
P := PChar(S);
Q := P + Length(S) - 1;
while P < Q do
begin
C := P^;
P^ := Q^;
Q^ := C;
Inc(P);
Dec(Q);
end;
end;