Calculate the factorial of a number without using any loop.

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In an interview someone asked me to calculate the factorial of a number without using any loop, nd even I tried but I was not able to complete it. Kindly help me how we can calculate factorial in c# without using any loop. Just Before posting this question I tried on google , but all the answers used loop.

So Once again I posted my query on my best tutorial resource.

Kindly help me.

Thanks.

Posted 3-Jun-14 18:51pm

StackQ

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ridoy 4-Jun-14 4:17am

If you will think it straightforward, then you can definitely answer it. Without loop it can be done in a smarter way, and guess what? That is called recursion!

4 solutions

Solution 2

Hi,

C#

public int fact(int n)
{
    if (n==0) return 1;
    else return n*fact(n-1)
}

Thanks,
Bh@gyesh

Posted 3-Jun-14 18:58pm

Bh@gyesh

Comments

Naz_Firdouse 4-Jun-14 1:33am

As per my knowledge, having if(n<=1) return 1; is the best approach.
Because it lessens one recursive call which gives the same result.

If we follow the above approach,
If n=1;
we call 1* fact(0)
where fact(0) returns 1 and then the end result is 1.

Instead if we use if(n <=1) return 1; condition....
it directly returns 1 in a single call.

I hope I am clear.

Solution 4

C#

int Factorial(int n)
{
     if (n <= 1)
          return 1;
     return n * Factorial(n - 1);
}

Posted 3-Jun-14 19:17pm

Manikandan10

Comments

[no name] 4-Jun-14 3:55am

Returns 1 for factorial of negative number. Not good.

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ArunRajendra · Accepted Answer · 2014-06-03T18:55:00

Solution 1

I am not sure this is the correct answer it should be possible using recursive fuction.

C#

int fact(int n)
{
    if(n==0)
       return 1;
    else
       return n * fact(n-1);
}

Posted 3-Jun-14 18:55pm

ArunRajendra

Updated 3-Jun-14 19:24pm

v2

Comments

Naz_Firdouse 4-Jun-14 1:33am

As per my knowledge, having if(n<=1) return 1; is the best approach.
Because it lessens one recursive call which gives the same result.

If we follow the above approach,
If n=1;
we call 1* fact(0)
where fact(0) returns 1 and then the end result is 1.

Instead if we use if(n <=1) return 1; condition....
it directly returns 1 in a single call.

I hope I am clear.

[no name] 4-Jun-14 1:47am

Good but wrong answer if -ve n.

Naz_Firdouse 4-Jun-14 3:10am

Thanks...but how the code mentioned in the solution works for negative numbers???

[no name] 4-Jun-14 1:44am

Unfortunately it won't like -ve n.

Naz_Firdouse 4-Jun-14 3:18am

The code mentioned in the solution throws "StackOverflowException" is negative values are passed to the function...

[no name] 4-Jun-14 3:32am

Of course it does. So it needs something like this as first line:
if(n < 0) return 0;
Then everyone happy.

Naz_Firdouse 4-Jun-14 3:46am

:)

DamithSL · Accepted Answer · 2014-06-03T19:07:00

Solution 3

you can use recursive method which calls itself so many times until being satisfied.
check below links for more information
Recursive methods using C#[^]
C# - Factorial With and With out using Recursive Functions[^]

Posted 3-Jun-14 19:07pm

DamithSL