70.Climbing Stairs

ou 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

Code:

最后一步可以选择

• 从i-1处迈一步
• 从i-2处迈两步

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