有表达式计算的逆波兰算法源码吗？

Question

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谢谢

Answer 1

unit calculator;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;type TStack=class
     private
       StackData:array[1..100] of string;
     public
       IsEmpty:boolean;
       TopPointer:integer;
       procedure Init;
       function Find(var data:string;i:integer):boolean;
       function Pop(var data:string):boolean;
       function Push(data:string):boolean;
end;type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    procedure StoreExpression(input:string);
    function TransformExpression:boolean;
    function Calculate(var Aresult:real):boolean;
  end;var
  Form1: TForm1;
  ExpressionStack,tempStack,NiPolandStack:TStack;implementation{$R *.dfm}procedure TForm1.FormCreate(Sender: TObject);
begin
  ExpressionStack:=TStack.Create;
  tempStack:=TStack.Create;
  NiPolandStack:=TStack.Create;
  ExpressionStack.Init;
  tempStack.Init;
  NiPolandStack.Init;
end;procedure TForm1.Button1Click(Sender: TObject);
var
  jg:real;
  input:string;
begin
  ExpressionStack.Init;
  tempStack.Init;
  NiPolandStack.Init;
  input:=edit1.Text;
  StoreExpression(input);
  if TransformExpression then
  begin
   if Calculate(jg) then edit2.Text:=floattostr(jg)
   else edit2.Text:='Syntax Error';
  end
  else edit2.Text:='Syntax Error';
end;function TStack.Find(var data:string;i:integer):boolean;
begin
  if (i>TopPointer) or (i<1) then begin
     result:=false;
     exit;
  end;  data:=StackData[i];
  result:=true;
end;procedure TStack.Init;
begin
  TopPointer:=0;
  IsEmpty:=True;
end;function TStack.Pop(var data: string): boolean;
var aData:string;
begin
  if not Find(aData,TopPointer) then begin
     result:=false;
     exit;
  end;
  data:=aData;
  stackData[TopPointer]:='';
  dec(TopPointer);
  if TopPointer<=0 then IsEmpty:=true else IsEmpty:=false;
  result:=true;end;function TStack.Push(data: string): boolean;
begin
  if TopPointer>=100 then begin
     result:=false;
     exit;
  end;
  isEmpty:=false;
  inc(TopPointer);
  StackData[TopPointer]:=data;
  result:=true;
end;
procedure TForm1.StoreExpression(input:string);
var temp:char;
    temp1:string;
    i:integer;
    v:string;
begin  v:='';
  for i:=1 to length(input) do begin
      temp:=input[i];
      if temp in ['+','-','*','/','(',')'] then begin
         if v<>'' then ExpressionStack.Push(v);
         ExpressionStack.Find(temp1,ExpressionStack.TopPointer);
         if (temp='-') and ((temp1='(') or (ExpressionStack.IsEmpty))then ExpressionStack.Push('0');
         ExpressionStack.Push(temp);
         v:='';
      end else begin
        v:=v+temp;
      end;
  end;
  if v<>'' then ExpressionStack.Push(v);
end;function TForm1.TransformExpression:boolean;
var i:integer;
    str:string;
    temp:string;
    value,code:integer;
begin
  result:=true;
  for i:=1 to ExpressionStack.TopPointer do begin
      ExpressionStack.Find(str,i);
      val(str,value,code);
      if code=0 then NiPolandStack.Push(str)
      else begin
        if str[1] in ['+','-','*','/','0','1','2','3','4','5','6','7','8','9','(',')'] then
        begin
         if (str='+') or (str='-') then begin
            while not tempStack.IsEmpty do begin
               tempStack.Find(temp,tempStack.TopPointer);
               if temp='(' then break;
               tempStack.Pop(temp);
               NiPolandStack.Push(temp);
            end;
         end;
         if (str='*') or (str='/') then begin
            while not tempStack.IsEmpty do begin
               tempStack.Find(temp,tempStack.TopPointer);
               if (temp='(') or (temp='-') or (temp='+') then break;
               tempStack.Pop(temp);
               NiPolandStack.Push(temp);
            end;
         end;
         if str=')' then begin
            result:=false;
            while not tempStack.IsEmpty do begin
               tempStack.Find(temp,tempStack.TopPointer);
               if (temp='(') then begin
                   result:=true;
                   tempStack.Pop(temp);
                   break;
               end;
               tempStack.Pop(temp);
               NiPolandStack.Push(temp);
            end;
         end;
         if str<>')' then tempStack.Push(str);
        end
        else 
         result:=false;
      end;
  end;  while not tempStack.IsEmpty do begin
     tempStack.Pop(temp);
     NiPolandStack.Push(temp);
  end;
  NiPolandStack.Find(temp,1);
end;function TForm1.Calculate(var Aresult:real):boolean;
var i:integer;
    temp:string;
    stra,strb:string;
    inta,intb,tempResult:real;
    code:integer;
begin
  Result:=false;
  ExpressionStack.Init;
  tempStack.Init;
  tempResult:=0;  for i:=1 to NiPolandStack.TopPointer do begin
      NiPolandStack.find(temp,i);
      case temp[1] of
       '+','-','*','/':begin
             if not tempStack.Pop(stra) then exit;
             if not tempStack.Pop(strb) then exit;
             val(stra,inta,code);
             if code<>0 then exit;
             val(strb,intb,code);
             if code<>0 then exit;
             if temp='+' then tempResult:=intb+inta;
             if temp='-' then tempResult:=intb-inta;
             if temp='*' then tempResult:=intb*inta;
             if temp='/' then begin
                if inta=0 then exit;
                tempResult:=intb/inta;
             end;
             tempStack.Push(floattostr(tempResult));
       end;
       else tempStack.Push(temp);
      end;
  end;
  tempStack.Pop(temp);
  if not tempStack.IsEmpty then exit;
  Aresult:=tempResult;
  result:=true;
end;
end.