191145685 发表于 2015-4-24 07:58:39

Python学习笔记(三)——迭代


[*]知识点


[*]迭代
  


[*]迭代
  什么是迭代呢?和递归又有什么区别呢?
  根据维基百科和网上的资料:
  迭代:迭代是重复反馈过程的活动,其目的通常是为了接近并到达所需的目标或结果。每一次对过程的重复被称为一次“迭代”,
  而每一次迭代得到的结果会被用来作为下一次迭代的初始值。
  如求1+2+3+4+5的和:
http://www.iyunv.com/JohnTsai/p/data:image/png;base64,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
  递归呢?指在函数的定义中使用函数自身的方法。也就是函数不停的调用自己直到满足一定条件。
  而用递归是怎样求1--5的和呢?
http://www.iyunv.com/JohnTsai/p/data:image/png;base64,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
  斐波那契数列的递归和迭代实现:



1 def fib(n):
2   if n>0:
3         if (n==1 or n==2):
4             return 1
5         else:
6             return fib(n-1)+fib(n-2)
7   else:
8          return -1
9 def fib_2(n):
10   if n
页: [1]
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