This document contains C code examples that demonstrate both recursive and non-recursive solutions to common problems: 1) Towers of Hanoi problem using recursive and non-recursive functions. 2) Finding the greatest common divisor (GCD) of two integers using recursive and non-recursive functions. 3) Calculating the factorial of a given integer using recursive and non-recursive functions.

1. /* Write C programs that use both recursive and non-recursive functions
To solve Towers of Hanoi problem.*/
#include<conio.h>
#include<stdio.h>
/* Non-Recursive Function*/
void hanoiNonRecursion(int num,char sndl,char indl,char dndl)
{
char stkn[100],stksndl[100],stkindl[100],stkdndl[100],stkadd[100],temp;
int top,add;
top=NULL;
one:
if(num==1)
{
printf("nMove top disk from needle %c to needle %c ",sndl,dndl);
goto four;
}
two:
top=top+1;
stkn[top]=num;
stksndl[top]=sndl;
stkindl[top]=indl;

2. stkdndl[top]=dndl;
stkadd[top]=3;
num=num-1;
sndl=sndl;
temp=indl;
indl=dndl;
dndl=temp;
goto one;
three:
printf("nMove top disk from needle %c to needle %c ",sndl,dndl);
top=top+1;
stkn[top]=num;
stksndl[top]=sndl;
stkindl[top]=indl;
stkdndl[top]=dndl;
stkadd[top]=5;
num=num-1;
temp=sndl;
sndl=indl;
indl=temp;
dndl=dndl;

3. goto one;
four:
if(top==NULL)
return;
num=stkn[top];
sndl=stksndl[top];
indl=stkindl[top];
dndl=stkdndl[top];
add=stkadd[top];
top=top-1;
if(add==3)
goto three;
else if(add==5)
goto four;
}
/* Recursive Function*/
void hanoiRecursion( int num,char ndl1, char ndl2, char ndl3)
{
if ( num == 1 ) {
printf( "Move top disk from needle %c to needle %c.", ndl1, ndl2 );
return;
}

4. hanoiRecursion( num - 1,ndl1, ndl3, ndl2 );
printf( "Move top disk from needle %c to needle %c.", ndl1, ndl2 );
hanoiRecursion( num - 1,ndl3, ndl2, ndl1 );
}
void main()
{
int no;
clrscr();
printf("Enter the no. of disks to be transferred: ");
scanf("%d",&no);
if(no<1)
printf("nThere's nothing to move.");
else
printf("Non-Recursive");
hanoiNonRecursion(no,'A','B','C');
printf("nRecursive");
hanoiRecursion(no,'A','B','C');
getch();
}

5. /* Write C programs that use both recursive and non-recursive functions
To find the GCD (greatest common divisor) of two given integers.*/
#include<stdio.h>
#include<conio.h>
#include<math.h>
unsigned int GcdRecursive(unsigned m, unsigned n);
unsigned int GcdNonRecursive(unsigned p,unsigned q);
int main(void)
{
int a,b,iGcd;
clrscr();
printf("Enter the two numbers whose GCD is to be found: ");
scanf("%d%d",&a,&b);
printf("GCD of %d and %d Using Recursive Function is %dn",a,b,GcdRecursive(a,b));
printf("GCD of %d and %d Using Non-Recursive Function is %dn",a,b,GcdNonRecursive(a,b));

6. getch();
}
/* Recursive Function*/
unsigned int GcdRecursive(unsigned m, unsigned n)
{
if(n>m)
return GcdRecursive(n,m);
if(n==0)
return m;
else
return GcdRecursive(n,m%n);
}
/* Non-Recursive Function*/
unsigned int GcdNonRecursive(unsigned p,unsigned q)
{
unsigned remainder;
remainder = p-(p/q*q);
if(remainder==0)
return q;
else

7. GcdRecursive(q,remainder);
}
/* Write C programs that use both recursive and non-recursive functions
To find the factorial of a given integer.*/
#include<stdio.h>
#include<conio.h>
unsigned int recr_factorial(int n);
unsigned int iter_factorial(int n);
void main()
{
int n,i;
long fact;
clrscr();
printf("Enter the number: ");
scanf("%d",&n);
if(n==0)

8. printf("Factorial of 0 is 1n");
else
{
printf("Factorial of %d Using Recursive Function is %dn",n,recr_factorial(n));
printf("Factorial of %d Using Non-Recursive Function is %dn",n,iter_factorial(n));
}
getch();
}
/* Recursive Function*/
unsigned int recr_factorial(int n) {
return n>=1 ? n * recr_factorial(n-1) : 1;
}
/* Non-Recursive Function*/
unsigned int iter_factorial(int n) {
int accu = 1;
int i;
for(i = 1; i <= n; i++) {
accu *= i;
}
return accu;
}