Question

How to reverse the order of the words in a string using recursion in Pascal

Answer 1

Program ReverseWordsInStringProgram;

function ReverseWords(var s :string; start :integer) :string;
var
  tmp :string;
begin
  if start <= length(s) then
  begin
    tmp := '';
    
    // get the word
    while (start <= length(s)) and (s[start] <> ' ') do
    begin
      tmp := tmp + s[start];
      Inc(start);
    end;
    
    // preserve the spaces
    while s[start] = ' ' do
    begin
      tmp := ' ' + tmp;
      Inc(start);
    end;
    
    // recursive call to get the next word and insert it before tmp
    ReverseWords := ReverseWords(s, start) + tmp;
  end else
    ReverseWords := '';
end;

var
  s :string;
begin
  s := 'aa bbb cccc ddddd';
  
  s := ReverseWords(s, 1);
  
  writeln(s);
end.


(*
run:

ddddd cccc bbb aa

*)

 

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