In C abs a - b does not return absolute value of negative number

0 votes
#include <stdio.h>
#include <cmath>

void update(int *a,int *b) {
    // Complete this function 
    (*a) = abs(*a + *b);
    (*b) = abs(*a - *b);   
}

int main() {
    int a, b;
    int *pa = &a, *pb = &b;

    scanf("%d %d", &a, &b);
    update(pa, pb);
    printf("%d\n%d", a, b);

    return 0;
}

I have the code below (from HackerRank C++ challenges). 

If I enter 4 and 5, it will return 9 and 4 as output instead of 9 and 1. 

I assumed it would be 4 - 5 = abs(-1) = 1. 

Why doesn't it operate that way?

Jun 22 in C++ by Nicholas
• 5,940 points
23 views

1 answer to this question.

0 votes

On the first line, you reallocated *a, and it is now utilising that new value on the second line. 

int origa = *a;
*a = abs(origa + *b);
*b = abs(origa - *b);

Alternatively, you may use tuples to get fancy:

std::tie(*a, *b) = std::make_tuple(abs(*a + *b), abs(*a - *b));

which just computes and packs up the values first, then unpacks them after all the reads are done.

answered Jun 27 by Damon
• 4,960 points

Related Questions In C++

0 votes
0 answers

Is there a default return value of C++ functions?

I'm amazed that a file with the  ...READ MORE

Jul 25 in C++ by Nicholas
• 5,940 points
25 views
0 votes
0 answers

Reverse a number without converting it to string in C++

I'm attempting to write a programme in C++ to reverse a number. It works well with numbers like 1234, but when I try to enter a number like 5430, it displays 345, and the same with numbers that begin with zero, such as 0234, which displays 432. Could someone please explain how to deal with zeros at the beginning and end of a sentence? I simply need to save the number without converting it to a string. #include<iostream> using namespace std; int main(){ ...READ MORE

Jun 30 in C++ by Nicholas
• 5,940 points
32 views
0 votes
0 answers

Inbuilt __gcd(A,B) function in C++

I recently learned about a c++ specia ...READ MORE

Jul 11 in C++ by Nicholas
• 5,940 points
24 views
0 votes
0 answers

What type of members can I add in a c++ abstract class

Hello, let's say I have an abstract class with a few pure abstract functions and a few classes that derive from it, and all of the data from these classes eventually becomes similar, I was wondering if it would be wise, or even possible, to declare a vector under protected in the abstract class to collect the data so something like that. class A { protected: vector <string> ...READ MORE

Jul 27 in C++ by Nicholas
• 5,940 points
27 views
0 votes
1 answer

What is a smart pointer and when should I use one?

A smart pointer is similar to a ...READ MORE

answered Jun 2 in C++ by Damon
• 4,960 points
29 views
0 votes
1 answer

Explanation of function pointers

It's a little perplexing. Function type and pointer to function type are distinct kinds (no more similar than int and pointer to int).  However, in virtually all cases, a function type decays to a reference to a function type.  In this context, rotting roughly refers to conversion (there is a difference between type conversion and decaying, but you are probably not interested in it right now). What matters is that practically every time you use a function type, you end up with a reference to the function type.  But take note of the nearly - almost every time is not always! And there are rare circumstances where it does not. typedef void(functionPtr)(int); functionPtr fun = function; This code tries to clone one function to another (not the pointer! the function!)  However, this is not feasible since functions in C++ cannot be copied.  The compiler does not let this, and I'm surprised you got it compiled (you say you got linker errors?) Now for the code: typedef void(functionPtr)(int); functionPtr function; function(5); function does ...READ MORE

answered Jun 21 in C++ by Damon
• 4,960 points
24 views
0 votes
0 answers

C++ pointer to objects

Is it always necessary in C++ to  ...READ MORE

Jun 27 in C++ by Nicholas
• 5,940 points
25 views
0 votes
0 answers

What are the differences between a pointer variable and a reference variable?

What distinguishes a reference variable from a ...READ MORE

Jul 11 in C++ by Nicholas
• 5,940 points
31 views
0 votes
1 answer

Cases of static and dynamic binding in C++

When an object's static type is used to associate it with a member function, this is known as static binding (understand the type of its class). When a pointer or reference is associated with a member function based on the dynamic type of the object, this is known as dynamic binding (understand the instance of the variable at runtime). Before continuing, keep in mind that dynamic binding only works with pointers, references, and virtual functions for the base class. Because everything needed to call the function is known at compile time, the first call is a static binding (also known as early binding). Derived1 d1(1, 10); d1.display_data(); You already know that the d1 instance is a Derived1 automatic variable, and that it will call the Derived1::display data method (). The first condition is incorrect: d1 is neither a pointer nor a reference. The second condition isn't acceptable:  There is no virtual Derived1::display data. The second call is for ...READ MORE

answered Jun 7 in C++ by Damon
• 4,960 points
31 views
0 votes
1 answer

Function default argument value depending on argument name in C++ [duplicate]

When the function is called with no argument for the corresponding parameter, the default argument is evaluated.  In a default argument, a parameter must not appear as a potentially evaluated expression.  A function's parameters declared before a default argument are in scope and can obscure the namespace and class member name. It provides the following example: int h(int a, ...READ MORE

answered Jun 7 in C++ by Damon
• 4,960 points
39 views
webinar REGISTER FOR FREE WEBINAR X
Send OTP
REGISTER NOW
webinar_success Thank you for registering Join Edureka Meetup community for 100+ Free Webinars each month JOIN MEETUP GROUP