loop problem?

[klamath23]

Yes, but isn't n*(n/4 + 0.5) exactly the same as (n *n)/4 + (n* 0.5) ?

if you know algebra then you should know this
c * (a + b) = c * a + c * b;
2 * (3 + 5) = 2 * 3 + 2 *5;
16 = 16 ;

[Zaccheus]

Indeed.

This works for human, this does'nt work in c#.

You are correct, because it is integer division!

It would wouk if he wrote n / 4.0.

[Mutant_Fruit]

6*(6/4+0.5) = 6 * 2 = 12

Ah, but you're performing integer division, not floating point division.

6/4 == 1

EDIT: It won't actually be completly accurate if you just change it to 4.0. You may end up with an answer like 11.99999999 instead of 12.

To round a floating point number to the *nearest* integer what you need to do is add 0.5 then just cast the float to int.

i.e.

double result = n * (n / 4.0 + 0.5);
int finalAnswer = (int)(result + 0.5);

Alternatively one of the other forms of the equation would be a better way of doing it.

[Zaccheus]

Well, as it happens 1.5, can be accurately reprepresented in binary - but I do take your point. Rounding errors are always an issue in floating point calculations.

[klamath23]

Well, as it happens 1.5, can be accurately reprepresented in binary - but I do take your point. Rounding errors are always an issue in floating point calculations.

There are better ways to do this problem
like this

int sumEven = 0;
for(int i =2; i<=n;n++)
{
if((i %  2)== 0)
sumEven+=i;
}

Console.WriteLine(" the sum of even numbers till n is:"+sumEven);

[torrud]

Indeed.



You are correct, because it is integer division!

It would wouk if he wrote n / 4.0.

You are right. It was just a typo mistake of me because I did not test the code. It means n / 4.0 on that part.

But I am understand the point of view for a rounding error. There is a simple solution. You have only to eliminate the fraction inside.

public uint Calculate(uint n)
{
    //ensure the number is an even number
    if (n % 2 == 1)
       n -= 1;
    //calculate sum without a loop because it is a arithmetic progression
    return n*(n + 2) >> 2;
}

That's it. There should no rounding error any longer.

[codeexpert123]

thanks for the help but I myself solved it