70.Climbing Stairs

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

class Solution:
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n<=2:
            return n
        list = [0,1,2]
        for i in range(3,n+1):
            list.append(list[i-2]+list[i-1])
        return list[n]