What's the logic behind this code.

Question

1.00/5 (2 votes)

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function fun(unsigned integer n)
begin
    result = 1
    while n != 0
    n = n - 1
    result = result + 2 * n
  end while
  return result
end

Assume that n > 0. What is the result computed by fun?

options:
A 2^n
B 2n − 1
C 2n − 2
*D n^2 − n + 1 (answer)
E n^2

What I have tried:

I have tried recursion. but don't understand this code.

Posted 1-Dec-21 21:24pm

Nobel Fix

Updated 1-Dec-21 21:38pm

OriginalGriff

v2

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Richard Deeming 2-Dec-21 3:52am

Funny - that code doesn't look anything like C, C++, or Java to me. Why have you tagged your question with three completely irrelevant tags?

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OriginalGriff · Accepted Answer · 2021-12-01T21:38:00

First off, indent your code correctly - it makes it a lot easier to see what is goign on:

function fun(unsigned integer n)
begin
    result = 1
    while n != 0
        n = n - 1
        result = result + 2 * n
    end while
    return result
end

Second, you only get recursion when a function directly or indirectly calls itself, as in the classic Factorial example:

function Factorial(int n)
begin
   if (n <= 1) return 1
   return n * Factorial(n - 1)
end

Your code doesn't do that, so it isn't recursive.

Instead it uses a loop, reducing the value of n each time round the loop, and exiting the loop only when n has reached zero.

So look at the code and generate each term that is added to result each time you go round. Write them down on a piece of paper, and it should be pretty obvious what it is doing, and how it works.

This is a simple bit of code, and you should be able to analyse it for yourself with a bit of effort - and that starts you "thinking the right way" about analysing more complex tasks. If we do that stage for you, it means you don't learn how to do that, and future tasks will become much harder as a result!