HackerRank Pointers in C solution

HackerRank Pointers in C problem solution – In this tutorial, we will solve the HackerRank Pointer in C problem and write a program solution for this problem.

Objective

In this challenge, you will learn to implement the basic functionalities of pointers in C. A pointer in C is a way to share a memory address among different contexts (primarily functions). They are primarily used whenever a function needs to modify the content of a variable that it does not own.

In order to access the memory address of a variable, var, prepend it with & sign. For example, &val returns the memory address of val.

This memory address is assigned to a pointer and can be shared among various functions. For example, int* p = &val will assign the memory address of val to pointer p. To access the content of the memory to which the pointer points, prepend it with a *. For example, *p will return the value reflected by val and any modification to it will be reflected at the source (val).

	void increment(int *v) {
        (*v)++; 
    }
      	int main() {
        int a;
        scanf("%d", &a);
        increment(&a);
        printf("%d", a);
    	return 0;      
    }     

Task

Complete the function void update(int *a,int *b). It receives two integer pointers, int* a and int* b. Set the value of a to their sum, and b to their absolute difference. There is no return value, and no return statement is needed.

• a’ = a+b
• b’ = |a+b|

Input Format

The input will contain two integers, a and b, separated by a newline.

Output Format

Modify the two values in place and the code stub main() will print their values.

Note: Input/ouput will be automatically handled. You only have to complete the function described in the ‘task’ section.

What is so special about pointer?

A pointer always used to hold the address of any other variable. so we don’t need to remember the value of any variable.

HackerRank Pointers in c solution

#include <stdio.h>

void update(int *a,int *b) {
    // Complete this function 
    *a=*a+*b;
    *b=abs(*a-(2**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;
}

Explanation

In the above program first, we declared a main() function. inside the main function, we have declared two integer variables a and b. after that we have declared a pointer pa and assigned the address of variable a as the value of pointer pa. and the same for the pointer pb.

After that using the scanf() function we read the two values from the input string and assigned them to variables a and b. after that we called the update() function with two input arguments of type pointer pa and pb.

What is inside the update() function?

In the update function, we just assigned the sum of values a and b to *a and then we calculated the absolute difference value to pointer b.

Second solution

#include <stdio.h>
#include <stdlib.h>

void update(int *a,int *b) {
    // Complete this function
    int t1, t2;
    t1 = *a + *b;
    t2 = abs(*a - *b);
    *a = t1;
    *b = t2;
}

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;
}