Find 2^(2^A) % B in C++

In this tutorial, we are going to write a program to evaluate the equation 2^(2^A) % B.

We are going to find the value of the equation using a recursive function. Let's see the steps to solve the problem.

• Write a recursive function that takes 2 arguments A and B.

  • If A is 1, then return 4 % B as 2^(2^1) % B = 4 % B.

  • Else recursively call the function with A-1 and b.

  • Return the result^2%B.

• Print the solution

Example

Let's see the code.

 Live Demo

#include <bits/stdc++.h>
using namespace std;
long long solveTheEquation(long long A, long long B) {
   // 2^(2^1) % B = 4 % B
   if (A == 1) {
      return (4 % B);
   }
   else {
      long long result = solveTheEquation(A - 1, B);
      return result * result % B;
   }
}
int main() {
   long long A = 37, B = 467;
   cout << solveTheEquation(A, B) << endl;
   return 0;
}

Output

If you execute the above code, then you will get the following result.

113

Conclusion

If you have any queries in the tutorial, mention them in the comment section.

Hafeezul Kareem

Published on 01-Feb-2021 11:45:08