6.37

/* 6.37 Iterative fibonacci function
   Deitel & Deitel C++ How to Program, 10th ed (Indian subcontinent adaptation)
   Visual Studio Community 2019
*/
#include <iostream>
using namespace std;

unsigned long long fibonacci( int num ) {
   unsigned long long fib{ 0 }, fib1{ 1 }, fib2{ 0 };
   int i{ 0 };
   if ( ( num == 0) || (num == 1 ) ) {
      return num;
   }
   for ( i = 2; i <= num; i++ ) {
      fib = fib1 + fib2;
      fib2 = fib1;
      fib1 = fib;
   }
   return fib;
}

int main() {
   for ( int count{ 0 }; count <= 55; count++ )
      cout << "fibonacci(" << count << ") = " << fibonacci(count) << endl;
}