leetcode(2)------Climbing Stairs

爬楼梯
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?
Note: Given n will be a positive integer.
Example1 :

Input: 2
Output: 2
Explanation: There are two ways to climb to the top.
1. 1 step + 1 step
2. 2 steps

Example 2:

Input: 3
Output: 3
Explanation: There are three ways to climb to the top.
1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step

Python代码实现：

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