Hey, a beginner needs Help

[Lucky7]

Hey i have been given a task:
Given a positive integer n. Find out if n! can be expressed as a sum of three consecutive numbers. Use a function that calculates a factorial in the solution.

int factorial(int n)
{
    if(n > 1)
        return n * factorial(n - 1);
    else
        return 1;
}

I know that i have to use this function, but i am stuck on how to check if its a sum of 3 numbers. Thanks for help in advance!

[Lucky7]

Im sorry its not a sum of three consecutive numbers but multiplication.

[Thomas1965]

You need to call the factorial function, store its value and then check if the value can be expressed as a sum of three consecutive numbers.

[Lucky7]

Oh thank you, but how do you check it?

[lastchance]

@Lucky7 - please make up your mind.

Do you want the SUM or the PRODUCT of three consecutive numbers?

If you want the SUM, then n! will be the sum of three consecutive numbers iff n >= 3.

If you want the PRODUCT, then check whether (r-1)r(r+1) equals n!, where
r = (int)( 1 + (n!)^1/3)
That would be the only possibility.

[Repeater]

A method to check is to check if the number is equal to 1*2*3. If it's not, check if it's equal to 2*3*4. Then check if it's equal to 3*4*5. Then check if it's equal to 4*5*6. Then check if it's equal to 5*6*7. Then check if it's equal to 6*7*8. Then check if it's equal to 7*8*9. Then check if it's equal to 8*9*10...

I'll leave you to work out when to stop checking, and also to work out how you can avoid having to always start at 1*2*3