UGCNET-July-2018-II-5

Question

Given below are three implementations of the swap() function in C++:

a	b	c
void swap (int a, int b) { int temp; temp=a; a=b; b=temp; } int main() { int p=0, q=1; swap(p, q); }	void swap (int &a, int &b) { int temp; temp=a; a=b; b=temp; } int main() { int p=0, q=1; swap(p, q); }	void swap (int *a, int *b) { int *temp; temp=a; a=b; b=temp; } int main() { int p=0, q=1; swap(&p, &q); }

Which of these would actually swap the contents of the two integer variables p and q?

• A. a only
• B. b only
• C. c only
• D. b and c only

Comments

c only..!

Answer 1

Only C.

A performs the swap on the local variables - the original variables are not changed.

B is incorrect declaration.

C is the only one which swaps correctly.

Comments

I also answered 'C' but official key show 'B' is the correct...
Can you explain ?
 

Caption

 

---

I don't think so that option (b) is incorrect declaration
Rather part (c) is incorrect because inside swap function definition there is incorrect assignment of values at the addresses of a and b

Thus answer should be option 2 i.e (b) only

If I am wrong then please correct me

Answer 2

It is not asked for c, it is asked for c++ and in c++ &a=b implies somewhat like pointer thing but not pointer. Hence B is correct option.moreover option c is incorrect as it is swapping pointers not the values.