6.13

每日一题https://leetcode-cn.com/problems/climbing-stairs/

爬楼梯，递归

class Solution(object):
    def climbStairs(self, n):
        num=[0,1,2]
        if(n==1):
            return 1
        if(n==2):
            return 2
        else:
            for i in range(3,n+1):
                num.append(num[i-1]+num[i-2])
            return num[n]