爬梯子问题与斐波那契数列

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?

一个长度为n的梯子，一次只能走1，2步，多少种走法能到顶部？

思路如下，n-1到n有2种方法，n-1走一步，或者n-2走两步

f（n)=f(n-1)+f(n-2)，著名的斐波那契数列

编程如下

class Solution(object):
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        a=1
        b=1
        for i in range(n):
            a,b=b,a+b
        return a