EX15.02.py

# 15.2 (Fibonacci numbers) Rewrite the fib function in Listing 15.2 using iterations.
# (Hint: To compute fib(n) without recursion, you need to obtain fib(n - 2)
# and fib(n - 1) first.) Let f0 and f1 denote the two previous Fibonacci numbers.
# The current Fibonacci number would then be f0 + f1. The algorithm can be
# described as follows:
# f0 = 0 # For fibs(0)
# f1 = 1 # For fib(1)
# for i in range(2, n + 1):
# currentFib = f0 + f1
# f0 = f1
# f1 = currentFib
# # After the loop, currentFib is fib(n)
# Write a test program that prompts the user to enter an index and displays its
# Fibonacci number.

n = eval(input("Enter a number: "))

f0 = 0
f1 = 1
fib = 0
for i in range(2, n + 1):
    fib = f0 + f1
    f0 = f1
    f1 = fib

print("The Fibonacci of", n, "is", fib)