'''lecture_35_fibonacci.py
Use recursion to compute the number of rabbits in year n.
Base cases: x1 = 0, x2 = 1
Oliver W. Layton
CS 151: Computational Thinking: Visual Media
Spring 2021
'''


def fibonacci(n):
    # Base case:
    if n == 1:
        return 0
    # Base case:
    if n == 2:
        return 1
    
    # Recursion
    return fibonacci(n-1) + fibonacci(n-2)


for i in range(1, 13):
    print('Year', i, ', rabbit population is:', fibonacci(i))

# fibonacci(3)
# - get into return fibonacci(n-1) + fibonacci(n-2)
# where return fibonacci(2) + fibonacci(1)
# fibonacci(2): return 1
# fibonacci(2): return 0 
# so back to fibonacci(3): fibonacci(2) + fibonacci(1) = 1 + 0 = 1