Algorithm-implementation/Matrix Exponential at master · Rohijulislam/Algorithm-implementation · GitHub

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#Matrix Exponential
#include<bits/stdc++.h>
using namespace std;
#define ll long long


void multiply(ll F[2][2], ll M[2][2])
{
    ll x =  F[0][0] * M[0][0] + F[0][1] * M[1][0];
    ll y =  F[0][0] * M[0][1] + F[0][1] * M[1][1];
    ll z =  F[1][0] * M[0][0] + F[1][1] * M[1][0];
    ll w =  F[1][0] * M[0][1] + F[1][1] * M[1][1];
    F[0][0] = x;
    F[0][1] = y;
    F[1][0] = z;
    F[1][1] = w;
}

/*
  function to calculate power of a matrix
 */
void power(ll F[2][2], int n)
{
    if (n == 0 || n == 1)
        return;
    ll M[2][2] = {{1,1},{1,0}};
    power(F, n / 2);
    multiply(F, F);
    if (n % 2 != 0)
        multiply(F, M);
}

/*
  function that returns nth Fibonacci number
 */
ll fibo_matrix(ll n)
{
    ll F[2][2] = {{1,1},{1,0}};
    if (n == 0)
        return 0;
    power(F, n - 1);
    return F[0][0]*1+F[0][1]*0;
}
int main()
{
    int n;
    while (1)
    {
        cout<<"Enter the integer n to find nth fibonnaci no:  ";
        cin>>n;
        cout<<fibo_matrix(n)<<endl;
    }
    return 0;
}