factorial

[Pragadheesh]

hi,
how to find factorial of a number(from 1 to 10) without using,
>loop statements like for, while, do while.
>conditional operators like if, case.
>arithmetic operators like + , - , * , % , /, ++, --.??!!

is there anyway to do so using logical operators.!!

 

[MetalheadGautham]

Why NOT use a loop ?

 

[Liverpool_fan]

Recursion.
*en.wikipedia.org/wiki/Recursion_(computer_science)

Why NOT use a loop ?

For learning Recursion I think.

EDIT: Though I admit even in recursion you have to exit it as well using conditions.

 

[sakumar79]

But even for recursion, we need both if statement and * operators...

Arun

 

[Pragadheesh]

i found this question in a C aptitude paper..!! its just you are given these constraints and to find the solution such that it satisfies them...!!

 

[Liverpool_fan]

But even for recursion, we need both if statement and * operators...

Arun

Yeah you are right.

I guess I don't have any idea then...

I hope someone comes with an answer, I am really curious of the answer, assuming the question is not wrong...

 

[dearboy009]

In which programming language do you want answer?

 

[Liverpool_fan]

In which programming language do you want answer?

i found this question in a C aptitude paper..!! its just you are given these constraints and to find the solution such that it satisfies them...!!

.

 

[Pragadheesh]

i came up with 2 solutions, one of which is quite silly.
1)

#include<stdio.h>

int factorial(int n)
{
	int a[] = {1,2,6,24,120,720,5040,40320,362880,3628800};
	return a[n-1];
}
int main()
{
	int num;
	printf("Enter a number between 1 and 10: ");
	scanf("%d",&num);
	printf("%d",factorial(num));
}

this might be funny..!![]

2)

#include <stdio.h>

int add(int a, int b)
{
int t1, t2, ab, bb, cb=0, orb=1, ans=0;

do {
	t1 = a >> 1; 
	t2 = t1 << 1;

	if (a==t2) ab=0; else ab=1;

	t1 = b >> 1;
	t2 = t1 << 1; 

	if (b==t2) bb=0; else bb=1;

	if (ab==1 && bb==1) { 
		if (cb==1) ans=ans | orb; 
		cb = 1; 
		}

	if ( ab!=bb ) { 
		if (cb==0) ans = ans | orb; 
		}

	if (ab==0 && bb==0) {
		if (cb==1) { 
		ans = ans | orb;
		cb=0;
				}
		}

	orb = orb << 1; 
	a = a >> 1;
	b = b >> 1;

	} while (a!=0 || b!=0);

if (cb==1) ans = ans | orb;

return ans;
}



int multiply(int x,int y)
{
	int result = 0, i = 0 , j=0;

	while((i=add(i,1)) <= y)
		result = add(result,x);

	return result;

}

int factorial(int x)
{
	if(x==1)
		return 1;
	else
		return multiply(x,factorial(x-1));

}


int main()
{
	int x;
	printf("Enter a number between 0 and 10: ");
	scanf("%d" , &x);
	printf("\nFactorial: %d\n" , factorial(x));
	return 0;
}

in the second solution i have used if conditions and while loops but no arithmetic operators involved.!

 

[sam_52136]

The first one is too good man..!
but what if some one asks you for factorial of 20 ?
hehe..

 

[Pragadheesh]

@sam_52136
thanx and ya, we need to use separate data structures of different techniques like BigInteger in java to find factorial of any number, as most data types cant hold such big values..

 

[kin.vachhani]

Can i have a hint...