Thats Insane - wrong memory setting by recursion???

[sk.Silvia]

thats insane, try to run this...you will get the most highest parent (node 0) as result, but try to run it with ShowMessage('val '+ValToStr+' res'+inttostr(result)); and you will get the right result...also you get the right result by adding result:=result;
but WHY?????????????????????????????????????

OMG WHY???????????????????

Delphi-Quellcode:

type TBinTree=class
      Value:integer;
      Left,Right: TBinTree;
      ...
      function FindMin(init:boolean):integer;
      end;
 

 function TBinTree.FindMin(init:boolean):integer;
      begin
      //ShowMessage('val '+ValToStr+' res'+inttostr(result));
      //result:=result;
      if value<result then
        begin
        result:=value;
        end;
      if init then result:=self.Value;
     
      if not(left=nil) then result:=left.FindMin(false);
      if not(right=nil) then result:=right.FindMin(false);
      end;

in prog -> ShowMessage(IntToStr(BinTree.MindMin(true)));

HOW CAN SHOWMESSAGE CHANGE THE RESULT OF A RECURSION????? AND WHY HAVE RESULT:=RESULT; THE SAME EFFECT??

[Dust Signs]

Line 17: there is an "exit" missing -_-

Dust Signs

[sk.Silvia]

iam sorry iam not getting it " Line 17: there is an "exit" missing -_- " Can you explain?

[Dust Signs]

//EDIT: Sorry, I was wrong.

Dust Signs

[JasonDX]

Zitat:

Zitat von sk.Silvia

Delphi-Quellcode:

 function TBinTree.FindMin(init:boolean):integer;
      begin
      //ShowMessage('val '+ValToStr+' res'+inttostr(result));
      //result:=result;
      if value<result then
        begin
        result:=value;
        end;
      if init then result:=self.Value;
     
      if not(left=nil) then result:=left.FindMin(false);
      if not(right=nil) then result:=right.FindMin(false);
      end;

in prog -> ShowMessage(IntToStr(BinTree.MindMin(true)));

HOW CAN SHOWMESSAGE CHANGE THE RESULT OF A RECURSION????? AND WHY HAVE RESULT:=RESULT; THE SAME EFFECT??

First rule of local variables: Do always initialize them before usage ;) You forgot that, and that might be the reason for the strange behaviour.

greetz
Mike

[xaromz]

Hello,

one problem (but not the only one I guess) with your code is that you haven't set the Result prior to comparing it to "Value". So "Result" is undefined.
I think you were trying to do something like this:

Delphi-Quellcode:

function TBinTree.FindMin: Integer; 
begin 
  Result := Value; // Assume current Value is lowest

  if Assigned(Left) then
    Result := Min(Left.FindMin, Result); // Get lowest value [current, left]

  if Assigned(Right) then
    Result := Min(Right.FindMin, Result); // Get lowest value [current, right]
end;

xaromz

[sk.Silvia]

yes your code is great xaromz, thats what i wanted

but i initialized the value of result, thnaks the init boolean (by the first run, the value of result was set to current), so it wasnt undefined, iam not getting it :(

[Dax]

You're not initializing the local variables at the very beginning of your method.. ;)

[xaromz]

Hello,

Zitat:

Zitat von sk.Silvia

yes your code is great xaromz, thats what i wanted

Thanks :) .

Zitat:

Zitat von sk.Silvia

but i initialized the value of result, thnaks the init boolean (by the first run, the value of result was set to current), so it wasnt undefined, iam not getting it :(

Your first piece of code was

Delphi-Quellcode:

 if value<result then

Here Result wasn't initialized. Your initializeation followed after that comparison.

Greets
xaromz

[sk.Silvia]

ok but ist the same also when i put

Delphi-Quellcode:

function TBinTree.FindMin(init:boolean):integer;
      begin
      if init then result:=self.Value;
      //ShowMessage('val '+ValToStr+' res'+inttostr(result));
      if value<result then
        begin
        result:=value;
        end;

      if not(left=nil) then result:=left.FindMin(false);
      if not(right=nil) then result:=right.FindMin(false);
      end;

value is always inicializes and result now too, but why the result changes besides on ShowMessage (again it gives the right value when i dont hide the showmessage dialog)

[JasonDX]

Zitat:

Zitat von sk.Silvia

ok but ist the same also when i put

Delphi-Quellcode:

function TBinTree.FindMin(init:boolean):integer;
      begin
      if init then result:=self.Value;
      //ShowMessage('val '+ValToStr+' res'+inttostr(result));
      if value<result then
        begin
        result:=value;
        end;

      if not(left=nil) then result:=left.FindMin(false);
      if not(right=nil) then result:=right.FindMin(false);
      end;

value is always inicializes and result now too, but why the result changes besides on ShowMessage (again it gives the right value when i dont hide the showmessage dialog)

Yea, because at the first call result will be initialized. But every recursive call after that does not initialize the result variable. You call the method with false as init-parameter, which tells not to initialize the variable. So once again: result is undefined ;)

greetz
Mike

[marabu]

Hi Silvia,

you might want to try out this:

Delphi-Quellcode:

uses
  Math;

function TBinTree.FindMin: Integer;
var
  minLeft, minRight: Integer;
begin
  if Assigned(left) 
    then minLeft := left.FindMin
    else minLeft := value;
  if Assigned(right) 
    then minRight := right.FindMin
    else minRight := value;
  Result := MinIntValue(value, minLeft, minRight);
end;

Kind regards

marabu