林登迈耶的藻类生长python实现

Example 1: Algae

Lindenmayer's original L-system for modelling the growth of algae.

variables : A B

constants : none

start  : A

rules  : (A → AB), (B → A)

which produces:

n = 0 : A

n = 1 : AB

n = 2 : ABA

n = 3 : ABAAB

n = 4 : ABAABABA

n = 5 : ABAABABAABAAB

n = 6 : ABAABABAABAABABAABABA

n = 7 : ABAABABAABAABABAABABAABAABABAABAAB

 

def algae(n):
    if n == 0:
        return 'A'
    if n == 1:
        return 'B'
    if n == 2:
        return 'A'
    else:
        return algae(n-1)+algae(n-2)
        
def all(n):
    result = ''
    for i in range(n+1):
        result+= algae(i)
    return result

def growth_of_algae(n):
    for i in range(n):
        print 'n = %d : %s' % (i, all(i))

n = int(raw_input("enter number of generation：\n"))
growth_of_algae(n)