putting a formula into a for loop

Question

I'm trying to put this formula into a loop

The function to put inside the loop

I've used if statements to give me a specific result if the input is zero, but if the input is one or higher, the for loop should run.

I was given a question regards recursion and supposed to execute it 3 different ways one of them using a loop that I've already made and runs but gives unexpected results.

public class Assignment5Recursion {
public static int puzzleLoop(int n) {
    int v=0;
    if(n>=1) {
        for(int i=1; i<=n+1; i++) {
            v = (2*i-1);
        }
        return ((2*n+1)+2*v);
    }
    else {
        return 1;
    }}}

if n is 1, the result should be 5, if n is 2, the result should be 13, if n is 3, the result should be 25, if n is 7, the result should be 113, but for some reason, I'm getting different outputs, so I'm assuming that I've set the loop wrong.

Answer 1

You need to make 2 changes.

1)The loop will run from i=1 to i=n+1 whereas you only require it to run till i=n.

So the for loop exit condition should either be i<n+1 or i<=n

2)The variable v is going to be replaced every run of the loop as it is getting assigned a new value every time.

So the value for v will always be v=2*(n+1)-1 according to your code.

You need to make this v += (2*i-1) so that the new value of v gets added to the old value to get sigma(sum).

Replacing your for loop as below will solve your problem.

for(int i=1; i<n+1; i++) {
        v += (2*i-1);
}

or

for(int i=1; i<=n; i++) {
        v = v+(2*i-1);
}