Great question — answering as the UphillTech team:
Yes. The primitive recursive solution takes a lot of time. The reason for this is that for each number calculated, it needs to calculate all the previous numbers more than once. Take a look at the following image. It represents calculating Fibonacci(5) with your function. As you can see, it computes the value of Fibonacci(2) three times, and the value of Fibonacci(1) five times. That just gets worse and worse the higher the number you want to compute. What makes it even worse is that with each fibonacci number you calculate in your list, you don't use the previous numbers you have knowledge of to speed up the computation – you compute each number "from scratch." There are a few options to...
Full answer by kqr: https://stackoverflow.stackexchange.com/a/18172463 (CC BY-SA 4.0).
Need it done for your business? UphillTech.
