Write C programs that use both recursive and non-recursive functions

1. To find the factorial of a given integer.
2. To find the GCD (greatest common divisor) of two given integers.

Description:

Factorial of a number is nothing but the multiplication of numbers from a given number to 1 Ex: 5! =5*4*3*2*1= 120

i) To find the factorial of a given integer. 

Algorithm:

Step 1: Start
Step 2: Read n value as integer
Step 3: Call function factorial (int n)
Step 4: End
        Call function factorial(int n)
             begin
        if (n = 0)
           return 1;
        else
           return (n * factorial(n - 1));
        end

Program:

#include <stdio.h>
#include <conio.h>
void main()
{
   int n, a, b;
   clrscr();
   printf("Enter any number\n");
   scanf("%d", &n);
   a = recfactorial(n);
   printf("The factorial of a given number using recursion is %d \n", a);
   b = nonrecfactorial(n);
   printf("The factorial of a given number using nonrecursion is %d ", b);
   getch();
}
int recfactorial(int x)
{
   int f;
   if(x == 0)
   {
    return(1);
   }
   else
   {
    f = x * recfactorial(x - 1);
    return(f);
   }
}
int nonrecfactorial(int x)
{
   int i, f = 1;
   for(i = 1;i <= x; i++)
   {
      f = f * i;
   }
   return(f);
}

Input & Output:

Enter any number
5
The factorial of a given number using recursion is 120 
The factorial of a given number using nonrecursion is 120

ii) To find the GCD (greatest common divisor) of two given integers

Algorithm:

Step 1: Start
Step 2: Read a, b values as integers
Step 3: Call function gcd (a, b) and assign it to res
Step 4: Print res
Step 5: Stop
        Called function gcd (a, b)
        begin
           while(v != 0)
           begin
              temp ← u MOD v;
              u ← v;
              v ← temp;
           end
           return(u);
        end

Program:

#include <stdio.h>
#include <conio.h>
void main()
{
   int a, b, c, d;
   clrscr();
   printf("Enter two numbers a, b\n");
   scanf("%d%d", &a, &b);
   c = recgcd(a, b);
   printf("The gcd of two numbers using recursion is %d\n", c);
   d = nonrecgcd(a, b);
   printf("The gcd of two numbers using nonrecursion is %d", d);
   getch();
}
int recgcd(int x, int y)
{
   if(y == 0)
   {
      return(x);
   }
   else
   {
     return(recgcd(y, x % y));
   }
}
int nonrecgcd(int x, int y)
{
   int z;
   while(x % y != 0)
   {
    z = x % y;
    x = y;
    y = z;
   }
   return(y);
}

Input & Output:

Enter two numbers a, b
3 6
The gcd of two numbers using recursion is 3
The gcd of two numbers using nonrecursion is 3