GATE Overflow | Programming | Test 1 | Question: 4

Question

Consider the following C functions:

int f1(int a, int b)
{
	while (a != b)
	{
		if(a > b)
			a = a - b;
		else
			b = b - a;
	}
	return a;
}
int f2(int a, int b)
{
	while (b != 0)
	{
		int t = b;
		b = a % b;
		a = t;
	}
	return a;
}
int f3(int a, int b)
{
	while (a != 0)
	{
		int t = a;
		a = b % a;
		b = t;
	}
	return b;
}

• A. All 3 functions return same value for all positive inputs
• B. f1 and f2 return same value for all positive inputs but not f3
• C. For some positive input all 3 functions return different values
• D. f2 and f3 return same value for all positive inputs but not f1

Answer 1

All three functions are same.
Function calculates GCD of numbers 'a' and 'b'.

Comments

Thanku so much sir ! for replying

input i taken a=5 & b=2

---

I just ran it 

arjun@Armi:~$ ./a.out 5 2
f1: 1
f2: 1
f3: 1

 

---

a=5 b=2

2!=0 [right]

t=2

b=a%b i.e 2

a=2

return 2

where i am wrong please correct me!

Answer 2

all 3 function are same

Answer 3

1.) gcd(a,b)

2.) gcd(b,a) ≈ gcd(a,b)

3.) gcd(a,b)