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How do I convert a simple loop to use recursion?

开发者 https://www.devze.com 2023-03-25 03:01 出处:网络
So I have this code: WRITELN( “input which member of series”) READ(n) p ← 2 prev1 ← 1 prev2 ← 1

So I have this code:

WRITELN( “input which member of series”) 
READ(n)
p ← 2
prev1 ← 1
prev2 ← 1
WHILE p IS LESS THAN n DO 
BEGIN
term ← prev1  +  prev2
prev2 ← prev1 
prev1 ← term 
p  ← p  +  1
END 
WRITELN (“term  =”, term)

Can someone help me rewrite the code so it works recursively (in either PHP or Pascal).

EDIT

N = 4

I'm using PASCAL. The problem is, the non-recursive code returns 3, while the recur开发者_如何学JAVAsive code returns 2.

This is my recursion code:

program Fibfun;

VAR
n,prev1,prev2,term : Integer;

FUNCTION sw(p:integer):integer;Begin
  if p < n then
      Begin
         term:= prev1 + prev2;
         prev2:=prev1;
         prev1:=term;
      End
  else
  Begin
   p:= 1 + sw(p);
   End;
sw:=term;
End;

Begin
prev1:=1;
prev2:=1;
term:=1;
writeln('Input number: ');
readln(n);

writeln('term ', sw(2));

readln;
End.


program test;     
var
 result : longint;
 num,i, error: integer;
 strnum: string;

function fib(n : integer) : longint;
begin
    if n <= 2 then fib := 1
    else fib := fib(n-2) + fib(n-1);
end;

begin
if ParamCount = 0 then
begin
  writeln('Enter integer:');
  readln(strnum);
  val(strnum,num,error);
end else 
begin
 val (ParamStr(1), num, error);
end;
for i := 1 to num do
begin
  result:= fib(i);
  writeln(i, ' : ', result);
end;

end.
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