20. Using recursion, (i) Find the factorial of a number (ii) Find Greatest Common Divisor (GCD) of two numbers (iii) To generate Fibonacci ~equence (iv) Reverse ’n’ characters.

#include<stdio.h> int gc,fibn=1;  char out[10]; main()

{

int n,sg,x,y,cur=1,prev=1; char ch,hc;

clrscr();

printf("enter the number to find its factorial\n"); scanf("%d",&n);

sg=factorial(n);

printf("factorial of a number is %d\n",sg); printf("************************************\n"); printf("\nenter the numbers to find GCD \n");  scanf("%d %d",&x,&y);

if(x<y) sg=gcd(x,y,x); else sg=gcd(x,y,y);

printf("\nGreatest common Divisor is %d\n",sg); printf("************************************\n");

printf("\nenter the number to find fibonocci series must less than 22 greater than 1\n"); scanf("%d",&x);

sg=fib(x,cur,prev,1);

printf("\n %d th fib value is %d\n",x,sg); printf("************************************\n"); printf("\nenter the characters to be reversed\n"); scanf("%s",ch);

n=strlen(ch); reverse(ch,n); getch(); return 0;

}

int factorial(int k) {

 

if(k==1) { return 1;

}

k=k*factorial(k-1); return(k);

}

int gcd(int a,int b,int i) { if((a%i==0) && (b%i==0)) return i;

else

gcd(a,b,--i);

}

int fib(int n,int cur,int prev,int count) { if(count>=n)

{

printf("%d ",fibn); return fibn;

}

printf("%d ",fibn); fibn=cur+prev; prev=cur; cur=fibn;

fib(n,cur,prev,count+1); return fibn;

}

reverse(char cl[],int n)

{

printf("%c",cl[n]); if(n<1) { out[n]=cl[n]; return 0;

}

reverse(cl,n-1);

out[n]=cl[n]; return 0;

}