list0715.cpp

teach yourself C++ in 21 days 第五版

// Listing 7.15 -  Demonstrates solving the nth
// Fibonacci number using iteration

#include <iostream>

unsigned int fib(unsigned int position);
int main()
{
   using namespace std;
   unsigned int answer, position;
   cout << "Which position? ";
   cin >> position;
   cout << endl;

   answer = fib(position);
   cout << answer << " is the ";
   cout << position << "th Fibonacci number. " << endl;
   return 0;
}

unsigned int fib(unsigned int n)
{
   unsigned int minusTwo=1, minusOne=1, answer=2;

   if (n < 3)
      return 1;

   for (n -= 3; n != 0; n--)
   {
      minusTwo = minusOne;
      minusOne = answer;
      answer = minusOne + minusTwo;
   }

   return answer;
}