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

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

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

(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);  swap (&p, &q);

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