Sunday, July 8, 2007

Write a C program to find the GCD of two numbers.

Here is a C program ....


#include < stdio.h >

int gcd(int a, int b);
int gcd_recurse(int a, int b);


int main()
{
printf("\nGCD(%2d,%2d) = [%d]", 6,4, gcd(6,4));
printf("\nGCD(%2d,%2d) = [%d]", 4,6, gcd(4,6));
printf("\nGCD(%2d,%2d) = [%d]", 3,17, gcd(3,17));
printf("\nGCD(%2d,%2d) = [%d]", 17,3, gcd(17,3));
printf("\nGCD(%2d,%2d) = [%d]", 1,6, gcd(1,6));
printf("\nGCD(%2d,%2d) = [%d]", 10,1, gcd(10,1));
printf("\nGCD(%2d,%2d) = [%d]", 10,6, gcd(10,6));

printf("\nGCD(%2d,%2d) = [%d]", 6,4, gcd_recurse(6,4));
printf("\nGCD(%2d,%2d) = [%d]", 4,6, gcd_recurse(4,6));
printf("\nGCD(%2d,%2d) = [%d]", 3,17, gcd_recurse(3,17));
printf("\nGCD(%2d,%2d) = [%d]", 17,3, gcd_recurse(17,3));
printf("\nGCD(%2d,%2d) = [%d]", 1,6, gcd_recurse(1,6));
printf("\nGCD(%2d,%2d) = [%d]", 10,1, gcd_recurse(10,1));
printf("\nGCD(%2d,%2d) = [%d]", 10,6, gcd_recurse(10,6));


getch();
getch();
return(0);
}

// Iterative algorithm
int gcd(int a, int b)
{
int temp;

while(b)
{
temp = a % b;
a = b;
b = temp;
}

return(a);
}


// Recursive algorithm
int gcd_recurse(int a, int b)
{
int temp;

temp = a % b;

if (temp == 0)
{
return(b);
}
else
{
return(gcd_recurse(b, temp));
}
}




And here is the output ...


Iterative
----------------
GCD( 6, 4) = [2]
GCD( 4, 6) = [2]
GCD( 3,17) = [1]
GCD(17, 3) = [1]
GCD( 1, 6) = [1]
GCD(10, 1) = [1]
GCD(10, 6) = [2]

Recursive
----------------
GCD( 6, 4) = [2]
GCD( 4, 6) = [2]
GCD( 3,17) = [1]
GCD(17, 3) = [1]
GCD( 1, 6) = [1]
GCD(10, 1) = [1]
GCD(10, 6) = [2]


Note that you should add error handling to check if someone has passed negative numbers and zero.

30 comments:

Sandeep Patra said...

a shorter code

int gcd (int a, int b) {
if(b == 0) {
return a;
} else {
return (gcd (b, a%b));
}
}

Priyanka said...

thanks a lot sandeep it actually helped a lot :-)

sushil said...

#include
main()
{
int n,m,a,b,gcd;
printf("\n enter two numbers ");
scanf("%d %d",&a,&b);
n=a;
m=b;
while(n!=m)
{
if(n>m)
n=n-m;
else
m=m-n;
}
gcd=n;

prinf("\n GCD of %d and %d is=%d",a,b,gcd);
}

karthik said...

sandeep your program is wrong i guess it wont work for 9 and 36 because gcd is 9 but 36-9=27

jhilik said...

sushil ....thanks....ur program worked....

sarah said...

nop! sushil ur program didn't work!

sarah said...

nop! sushil ur program didn't work!

shishir said...

#include
int GCD(int x, int y);
void main() {
int a,b;
scanf("%d/n",&a);
scanf("%d",&b);
printf("the GCD Is:%d", GCD(a,b));

}
int GCD(int x, int y)
{
if(x==y)
return x;
else if (x>y) {
return GCD(x-y,y);
}
else
return GCD(y-x,x);
}

cshir said...

i meant #include

This should work.
Thanks,
Shishir

cshir said...

for some reason, the library function is not getting included. please include the standard library function, stdio.h

dhiraj said...

ya! thnx cshir,u gave us the actual prgrm.....thax again.

SHAILY said...

Make a program for finding GCD of two numbers .... then tell!!!

SHAILY said...

Sorry! I meant make a program of finding GCD of two polynomials of degree m,n( m<=n) then tell

Anonymous said...

#include
int gcd(int a,int b);
main()
{
int a,b,i;
scanf("%d %d",&a,&b);
i=gcd(a,b);
printf("%d\n",i);
return 0;
}
int gcd(int a,int b)
{
if(a==0 || a==b)
return b;
if(b==0)
return a;
if(a>b)
return (gcd(a-b,b));
if(b>a)
return (gcd(a,b-a));
}

Anonymous said...

Here's a program showing three different versions, two of which were found here and integrated in


#include

//Checks two numbers and outputs their greatest common divisor
/*
int gcd(int dividend, int divisor)
{
int rem = -1;
while(rem != 0)
{
rem = dividend % divisor;
dividend = divisor;
if(rem != 0)
divisor = rem;
}
}
*/
/*
int gcd(int a, int b)
{
int temp;

while(b)
{
temp = a % b;
a = b;
b = temp;
}

return(a);
}
*/

/*int gcd(int a, int b)
{
int temp;

temp = a % b;

if (temp == 0)
{
return(b);
}
else
{
return(gcd(b, temp));
}*/
}

int main()
{
int a, b;

printf("Enter two numbers: ");

scanf("%i %i", &a, &b);
// if(gcd(a, b) != 1)
printf("GCD = %i \n", gcd(a, b));

}

riya said...

thanks lot. really it makes very helpful to me.

suruchi said...

sushil,your program works .......even it works for 9 nd 36 bt i can,t understand how did it works???
because 36-9=27 bt gcd is 9.it gives 9 bt can u plz tell me how???..

Devanshi gor said...

This really helped me... thanks..

Devanshi gor said...

This really helped me... thanks...

Mohammed Farhan said...

Use #include

Mohammed Farhan said...

#include

Mohammed Farhan said...

Its soo lengthy

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Rachumallu said...

ur programme is very easy.if u want effective than this login smart programmers

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