Python3解leetcode Maximum SubarrayClimbing Stairs

问题：

 

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.

 

Example 1:

 

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

思路：
上台阶问题，一次只能上一个或两个台阶，问总共有n个台阶，一共有多少种走法。
明显的动态规划问题，
当要到达地n个台阶的时候，有两种走法，第一种是从N-1个台阶走一步，第二种是N-2个台阶走两步。

class Solution:
    def climbStairs(self, n: int) -> int:
        if n ==1 :return 1
        count= [0 for i in range(n)]
        count[0] = 1
        count[1] = 2
        for i in range(2,n):
            count[i] = count [i-1] + count[i-2]
        return count[n-1]