c code to find and print factorial of a number, three methods are given, first one uses for loop, second uses a function to find factorial and third using recursion. Factorial is represented using '!', so five factorial will be written as (5!), n factorial as (n!). Also
n! = n*(n-1)*(n-2)*(n-3)...3.2.1 and zero factorial is defined as one i.e. 0! = 1.
Factorial program in c using for loop #include < stdio.h >
int main()
{
int c, n, fact = 1;
printf("Enter a number to calculate it's factorial\n");
scanf("%d", &n);
for (c = 1; c < = n; c++)
fact = fact * c;
printf("Factorial of %d = %d\n", n, fact);
return 0;
}
Output:
Enter any to calculate this factorial: 6
Factorial of 6 is : 720
Factorial program in c using function
#include < stdio.h >
long factorial(int);
int main()
{
int number;
long fact = 1;
printf("Enter a number to calculate it's factorial\n");
scanf("%d", & number);
printf("%d! = %ld\n", number, factorial(number));
return 0;
}
long factorial(int n)
{
int c;
long result = 1;
for (c = 1; c < = n; c++)
result = result * c;
return result;
}
Factorial program in c using recursion
#include < stdio.h >
long factorial(int);
int main()
{
int n;
long f;
printf("Enter an integer to find factorial\n");
scanf("%d", & n);
if (n > 0)
printf("Negative integers are not allowed.\n");
else
{
f = factorial(n);
printf("%d! = %ld\n", n, f);
}
return 0;
}
long factorial(int n)
{
if (n == 0)
return 1;
else
return(n * factorial(n-1));
}
Remarks: Recursion is a technique in which a function calls itself, for example in above code factorial function is calling itself. To solve a problem using recursion you must first express its solution in recursive form.
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