/*--- fibonacci.cpp --------------------------------------------------------
   Program to compute the Fibonacci function both
   iteratively and recursively.

   Input:  a positive integer x
   Output: the x-th Fibonacci number

  Written by:   Larry R. Nyhoff
   
  Written for:  Lab Manual for ADTs, Data Structures, and Problem
                Solving with C++, 2E

                            Lab #9.1
                                                          
  Add your name here and other info requested by your instructor.

  -------------------------------------------------------------------------*/

#include <iostream>
using namespace std;


unsigned iterFibonacci(unsigned n);
/*---------------------------------------------------------
   An iterative (nonrecursive) Fibonacci number calculator
  
   Precondition:  n >= 1.
   Postcondition: n-th Fibonacci number is returned.
 ------------------------------------------------------------*/

unsigned recFibonacci(unsigned n);
/*---------------------------------------------------------
   A recursive) Fibonacci number calculator
  
   Precondition:  n >= 1.
   Postcondition: n-th Fibonacci number is returned.
 ------------------------------------------------------------*/

int main()
{
  unsigned x;

  cout << "Please enter a positive integer: ";
  cin >> x;
  
  // Now print the result of the iterative version of the function
  cout << "Iterative fib(" << x << ") = " << iterFibonacci(x) << endl;

  // Now print the result of the recursive version of the function
  // cout << "Recursive fib(" << x << ") = " << recFibonacci(x) << endl;
}


//--- Definition of iterFibonacci()
unsigned iterFibonacci(unsigned n)
{
  int
    nextFib = 1,        // the next Fibonacci number to be calculated
    previousFib = 1,    // the Fibonacci number before it
    beforePreviousFib;  // the Fibonacci number before that one

  for (int i = 3; i <= n; i++)
    {
      // First, update the previous and before previous values
      beforePreviousFib = previousFib;
      previousFib = nextFib;

      // Then compute the next Fibonacci value
      nextFib = previousFib + beforePreviousFib;
    }

  return nextFib;
}


//--- Definition of recFibonacci()
unsigned recFibonacci(unsigned n)
{
  // Add statements for RecFibonacci() here
}