Python Walking Stairs Problem Solution Example

# -*- coding:utf-8 -*-
#!python3
'''
Downstairs Problem. There are h steps to walk from upstairs to downstairs, and there are two ways to walk each step:
Walking 1 step and walking 2 steps, ask how many walkable options there are. Programming with recursive and iterative ideas
'''
'''
Analysis: The problem can be considered in reverse, in terms of whether the last time you took 1 step or 2 steps.
'''
def take_stairs_recursive(n):
  if n == 1:
    return 1
  elif n == 2:
    return 2
  else:
    return take_stairs_recursive(n-1)+take_stairs_recursive(n-2)
'''
It's actually the Fibonacci sequence
'''
def take_stairs(n):
  if n == 1:
    return 1
  if n == 2:
    return 2
  a,b = 1,2
  result = 0
  for i in range(3,n+1):
    result = a + b
    a = b
    b = result
  return result
print(take_stairs_recursive(10))
print(take_stairs(10))