Set a variable without using Arithmetic, Relational or Conditional Operator

Given three integers a, b and c where c can be either 0 or 1. Without using any arithmetic, relational and conditional operators set the value of a variable x based on below rules –

If c = 0
    x = a
Else // Note c is binary
    x = b.

Examples:

Input: a = 5, b = 10, c = 0;
Output: x = 5

Input: a = 5, b = 10, c = 1;
Output: x = 10

Solution 1: Using arithmetic operators
If we are allowed to use arithmetic operators, we can easily calculate x by using any one of below expressions –

x = ((1 - c) * a) + (c * b)

OR

x = (a + b) - (!c * b) - (c * a);

OR

x = (a * !c) | (b * c);

#include <iostream>
using namespace std;

int calculate(int a, int b, int c)
{
    return ((1 - c) * a) + (c * b);
}

int main()
{
   int a = 5, b = 10, c = 0;

   int x = calculate(a, b, c);
   cout << x << endl;

   return 0;
}

Output:

5

Solution 2: Without using arithmetic operators
The idea is to construct an array of size 2 such that index 0 of the array stores value of variable ‘a’ and index 1 value of variable b. Now we return value at index 0 or at index 1 of the array based on value of variable c.

#include <iostream>
using namespace std;

int calculate(int a, int b, int c)
{
   int arr[] = {a, b};
   return *(arr + c);
}

int main()
{
   int a = 5, b = 10, c = 1;

   int x = calculate(a, b, c);
   cout << x << endl;

   return 0;
}

Output:

10

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