ISRO2017-41

Question

What is the output of the C++ program?
 

#include <iostream>
using namespace std;

void square(int *x){
    *x = (*x)++ * (*x);
}

void square(int *x, int *y){
    *x = (*x) * --(*y);
}

int main()
{
  int number = 30;
  square(&number, &number);
  cout<<number;
  return 0;
}

• A. 910
• B. 920
• C. 870
• D. 900

Comments

it will give the error:

*x= (*x)++ * *(*x);  // error , since only single indirection allowed

*x= (*x)++  * (*x); // statement should be like this. Ans=870

Answer 1

Option C 870

Comments

@Purvi Agrawal

plz explain the answer instead of just selecting the option, so that it will be helpful for future aspirants.

Answer 2

From main function, square function is called with two arguments => square(&number, &number);

Hence, the second definition of square will be overloaded. And it has:

*x= (*x) * --(*y);                where *x = 30 and *y = 30

-- (decrement) operator has the higher precedence than * (multiplication).

hence,

*x = 30 * 29

*x = 870

And the call to square function was a call by reference. Address of parameters was passed. So the value of number will be changed. And output will be 870.

 
And ofcourse, the line in first definition of square is typed wrongly. It should be:
*x= (*x)++ * (*x);    // In exam paper, it was correct.