Climbing Stairs
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?
python code：
class Solution:
# @param {integer} n
# @return {integer}
def climbStairs(self, n):
if n<=0: #illegal input
return 0
else:
if n==1:
return 1
if n==2:
return 2
a,b=1,2
for i in range(3,n+1):
a,b=b,a+b #斐波拉契数列，卡塔兰数？
return b
leetcode Climbing Stairs python
原文：http://www.cnblogs.com/bthl/p/4574526.html