C++ Variadics in C++ – Solution in Hacker Rank - hackerranksolutions8

 

Problem

A template parameter pack is a template parameter that accepts zero or more template arguments (non-types, types, or templates). To read more about parameter pack, click here.

Create a template function named reversed_binary_value. It must take an arbitrary number of bool values as template parameters. These booleans represent binary digits in reverse order. Your function must return an integer corresponding to the binary value of the digits represented by the booleans. For example: reversed_binary_value<0,0,1>() should return 4.

---

Input Format :

The first line contains an integer, t, the number of test cases. Each of the t subsequent lines contains a test case. A test case is described 2 as space-separated integers, x and y, respectively.

• x is the value to compare against.
• y represents the range to compare: 64*y to 64*y+63 .

Constraints :

• 0 <= x <= 65535
• 0 <= y <= 1024
• The number of template parameters passed to reversed_binary_value will be < 16

Output Format :

Each line of output contains 64 binary characters (i.e., 0’s and 1’s). Each character represents one value in the range. The first character corresponds to the first value in the range. The last character corresponds to the last value in the range. The character 1 is if the value in the range matches X; otherwise, the character is 0.

---

Sample Input :

2
65 1
10 0

Sample Output :

0100000000000000000000000000000000000000000000000000000000000000
0000000000100000000000000000000000000000000000000000000000000000

Explanation :

The second character on the first line is a 1, because the second value in the range 64..127 is 65 and x is 65.
The eleventh character on the second line is a 1, because the eleventh value in the range 0..63 is 10 and x is 10.All other characters are zero, because the corresponding values in the range do not match x.

---

Solution :

//C++ Variadics in C++ - Hacker Rank Solution
#include <iostream>
using namespace std;

// Enter your code for reversed_binary_value<bool...>()
/* C++ Variadics in C++ - Hacker Rank Solution START */
template <bool a> int reversed_binary_value() { return a; }

template <bool a, bool b, bool... d> int reversed_binary_value() {
  return (reversed_binary_value<b, d...>() << 1) + a;
}
/* C++ Variadics in C++ - Hacker Rank Solution END */

template <int n, bool...digits>
struct CheckValues {
  	static void check(int x, int y)
  	{
    	CheckValues<n-1, 0, digits...>::check(x, y);
    	CheckValues<n-1, 1, digits...>::check(x, y);
  	}
};

template <bool...digits>
struct CheckValues<0, digits...> {
  	static void check(int x, int y)
  	{
    	int z = reversed_binary_value<digits...>();
    	std::cout << (z+64*y==x);
  	}
};

int main()
{
  	int t; std::cin >> t;

  	for (int i=0; i!=t; ++i) {
		int x, y;
    	cin >> x >> y;
    	CheckValues<6>::check(x, y);
    	cout << "\n";
  	}
}