Having troubles with math

Question

I met this question some hours ago while completing challenges, and I find it very hard to make all the visualization in my head without taking 2 or 3 minutes, probably because I'm bad at math in general but ..

Is there some formula for solving this without having to imagine visually all the five loop iterations and their values?

// arg = 5

public static int myFunc(int arg)
{
int result = 0;

for (int i = 0; i < arg; i++)
{
result = result + i;

}

return result;
}

Answer 1

Also, very generally, when arg is even you could use:
(1+arg)*(arg/2)
when arg is odd you could use:
(1+arg)*((arg-1)/2)+median(1 to arg)

the above assumes the condition <=, otherwise you would just substitute arg-1 for arg in the above pseudo code

Answer 2

First you have to note that the loop will iterate up to 4 from 0.result is being incremented with the values 0 to 4 and the resulting sum is output....So basically you would just have to add
(0+1+2+3+4)
hope it answers your question.

Answer 3

Thanks but I think I found the formula Console.WriteLine("\tAnswer is equal to " + ((arg * (arg - 1)))/2);

Answer 4

For instance, when I pass 5 as an argument, I already know the answer is not going to be less than 5 because the loop ends at 4 < 5 and then ++, so I already know half of the answer how I find the other half?

Answer 5

Also if your for loop works with '<=' instead of '<', you should replace the (-1) in the formula with (+1) and it will work