70. 爬楼梯
class Solution:
def climbStairs(self, n):
"""
:type n: int
:rtype: int
"""
condition = [0] * (n + 1)
condition[0] = 1
condition[1] = 1
for i in range(2, n+1):
condition[i] = condition[i-1] + condition[i-2]
return condition[n]