Write a single pascal program that contains a function that calculates the addition of all numbers from 1 to the numbers passed to it

Answer 1

You can use the math shortcut: N * (N+1)/2, as proved by induction.

As an example, for N=5:: 1+2+3+4+5 = 15 vs 5*(5+1)/2 = 5*6/2 = 30/2 = 15

I have a feeling your instructor wants to see the for loop. So I included the

shortcut as a CHECK. Here's the listing:

--------------------------------------------------------------------------------------------------------------------

Program SumFirstNIntegers (input,output);

{*********************************************************}

Function SumFirstNInteger ( N : integer) : longint;

var iLoop : integer;

SumReturn : longint;

Begin

SumReturn:=0;

For iLoop:= 1 to N do

SumReturn := SumReturn + iLoop;

if (sumReturn= ( N * (N+1)/2)) then

SumFirstNInteger:=SumReturn

else begin

SumFirstNInteger:=-1;

writeln(' Calcualtion Fails ');

end;

end;

{**********************************************************}

VAR

N : integer;

BEGIN

{* uncomment this for input *}

repeat

write(' Please input N :>');

readln(N);

until (N>0);

{* comment this out if using input *}

{N:=5;}

writeln(SumFirstNInteger(N));

END.