Data update

Task/Fibonacci-sequence/Pascal/fibonacci-sequence-2.pas

@@ -1,8 +1,17 @@
-function fib(n: integer): integer;
- begin
-  if (n = 0) or (n = 1)
-   then
-    fib := n
-   else
-    fib := fib(n-1) + fib(n-2)
- end;
+function fib(n: integer):longInt;
+const
+  Sqrt5 = sqrt(5.0);
+  C1 = ln((Sqrt5+1.0)*0.5);//ln( 1.618..)
+//C2 = ln((1.0-Sqrt5)*0.5);//ln(-0.618 )) tsetsetse
+  C2 = ln((Sqrt5-1.0)*0.5);//ln(+0.618 ))
+begin
+  IF n>0 then
+  begin
+    IF odd(n) then
+      fib := round((exp(C1*n) + exp(C2*n) )/Sqrt5)
+    else
+      fib := round((exp(C1*n) - exp(C2*n) )/Sqrt5)
+  end
+  else
+    Fibdirekt := 0
+end;