Calculate factorials in C++ by function
I wrote this code :
int fact (int A)
{
int B ;
B= A*(A-1);
return B;
}
int main ()
{
int x;
cout <<"Enter number to calulate its factorial :"<<endl;
cin >> x ;
cout << fac (x);
}
Have you ever tried to google it before posting there?
int factorial(int n)
{
if (n < 0 ) {
return 0;
}
return !n ? 1 : n * factorial(n - 1);
}
Your fact function just computes factorial for one time. You should do something resursively like:
int fact (int A)
{
if (A <= 1) {
return 1;
}
return A*fact(A-1);
}
or if you want it in iterative way then you should do the following:
int fact (int A)
{
int B = 1, i = 2;
for (; i<=A; i++) {
B = B*i;
}
return B;
}
And why din't you search it instead.
anyway...
int n, count;
unsigned long long int factorial=1;
cout<<"Enter an integer: ";
cin>>n;
if ( n< 0)
printf("Error!!! Factorial of negative number doesn't exist.");
else
{
for(count=1;count<=n;++count) /* for loop terminates if count>n */
{
factorial*=count; /* factorial=factorial*count */
}
cout<<factorial;
}
First of all this has nothing to do with C++ ( as your question says ). This is specific to alogorithms and they can be employed in any language.
You can use below example for your reference.
int fact (int A)
{
if (A == 0) {
return 1;
}
return A*fact(A-1);
}
Since you're using C++ rather than C, I'd simply go with a template function. Bonus for this: due to expansion/implementation at compile time, your code will be highly optimized and essentially as fixed as possible with little to no overhead:
// First the generic template for pretty much all numbers
template <unsigned int X>
unsigned int factorial() {
return X * factorial<X - 1>();
}
// Now the specialization for the special case of 0
template <>
unsigned int factorial<0>() {
return 1;
}
For example, to calculate the factorial of 5, you'd just call factorial<5>(). With optimizations enabled, this will result in just 120. Unfortunately this is not possible with dynamic variables.
