sum of n natural no & factorialusing recursion model

sum of N nos using rm

#include<stdio.h>
int f1(int);
int main()
{
  int k,n;
  printf("Enter a no");
  scanf("%d",&n);
  k=f1(n);
  printf("%d",k);
  return 0;
}
int f1(int a)
{
    int s;
    if(a==1)
    return (1);
    s=a + f1(a-1);
    return (s);
}


factorial of N using recursion model


#include<stdio.h>
int f1(int);
int main()
{
  int k,n;
  printf("Enter a no");
  scanf("%d",&n);
  k=f1(n);
  printf("%d",k);
  return 0;
}
int f1(int a)
{
    int s;
    if(a==0)
    return (1);
    s=a*f1(a-1);
    return (s);
}


first N natural print using recursion method




#include<stdio.h>
void f1(int);
int main()
{
  int n;
  printf("Enter a no");
  scanf("%d",&n);
  f1(n);
  return 0;
}
void f1(int n)
{
    if(n>1)
    {
      f1(n-1);
      printf(" %d",n);
    }
    if(n==1)
    printf("1");
}