python 案例006 （斐波那契数列）

#! /usr/bin/python
# -*- coding:utf-8 -*-

"""
an interesting topic Fibonacci sequence
"""

#the method we know how to solve this issue  ----recursion

def fib(n):
    if n ==1 or n ==2 :
        return 1
    else:
        return fib(n-1)+ fib(n-2)
n = 10
print "Fibonacci sequence value of %d is : " % n,fib(n)

# 有点意思

def fibv2(n):
    a,b =1,1
    for i in range(n-1):  # if n = 10 then 10 -1 = 9 range(9) ,recursion 9 times
        a,b= b,a+b         # ？？？
        print 'a=',a,'b=',b
    return a
print fibv2(10)
"""
Fibonacci sequence value of 10 :  55
a= 1 b= 2
a= 2 b= 3
a= 3 b= 5
a= 5 b= 8
a= 8 b= 13
a= 13 b= 21
a= 21 b= 34
a= 34 b= 55
a= 55 b= 89
55
"""