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

Python

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class Solution(object):
    def __init__(self):
        self.temp = {1: 1, 2: 2}
 
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n in self.temp:
            return self.temp[n]
        else:
            result = self.climbStairs(n-1)+self.climbStairs(n-2)
            self.temp[n] = result
        return result

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