(You need to have first completed Programming Project 13.6 to work on this project.) When computing a Fibonacci number using the most straightforward recursive function definition, the recursive solution recomputes each Fibonacci number too many times. To compute F_i+2 = F_i + F_i+1, it computes all the numbers computed in F_i a second time in computing F_i+1 . You can avoid this by saving the numbers in an array while computing F_i. Write another version of your recursive Fibonacci function based on this idea. In the recursive solution for calculating the N th Fibonacci number, declare an array of size N. Array entry with index i stores the i^th ( ) Fibonacci number as it is computed the first time. Then use the array to avoid the second (redundant) recalculation of the Fibonacci numbers. Time this solution as you did in Programming Project 13.6 , and compare it to your results for the iterative solution.