问题描述
You are climbing a stair case. It takes n steps to reach to the top.
Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
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补充说明：
模拟上台阶，每次能上1级或者2级台阶，给定你一个台阶个数，问有多少种上台阶的方式。
方案分析
- 这个问题一眼就让笔者回忆到上学和刚毕业找工作的那段日子了。这个问题像不像斐波那契数列？
- 唯一与斐波那契数列不同的是n=1和n=2的时候。
- 啥也不说了，上代码，不要用递归。
python实现
class Solution(object):
def climbStairs(self, n):
"""
:type n: int
:rtype: int
"""
if n==1:
return 1
if n==2:
return 2
prev = 2
p_prev = 1
result = 0
for i in range(n-2):
result = prev + p_prev
p_prev = prev
prev = result
return result
