C++ Program to Implement Euler Theorem

This is a C++ Program which demonstrates the implementation of Euler Theorem. The number and modular must be coprime for the modular multiplicative inverse to exist.

Algorithm

Begin
   Take input to find modular multiplicative inverse
   Take input as modular value
   Perform inverse array function:
   modInverse(x + 1, 0);
   modInverse[1] = 1;
   for i = 2 to x
      modInverse[i] = (-(y / i) * modInverse[y mod i]) mod y + y
   return modInverse
End

Example Code

#include <iostream>
#include <vector>
using namespace std;
vector<int> inverseArray(int x, int y) {
   vector<int> modInverse(x + 1, 0);
   modInverse[1] = 1;
   for (int i = 2; i <= x; i++) {
      modInverse[i] = (-(y / i) * modInverse[y % i]) % y + y;
   }
   return modInverse;
}
int main() {
   vector<int>::iterator it;
   int a, m;
   cout<<"Enter number to find modular multiplicative inverse: ";
   cin>>a;
   cout<<"Enter Modular Value: ";
   cin>>m;
   cout<<inverseArray(a, m)[a]<<endl;
}

Output

Enter number to find modular multiplicative inverse: 26
Enter Modular Value: 7
7