Problem

You are climbing a staircase. It takes n steps to reach the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

Example 1:

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

Example 2:

Input: n = 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

Solution

It's Fibonacci!

class Solution(object):
    def __init__(self):
        self.dic = {1:1, 2:2}
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n not in self.dic:
            self.dic[n] = self.climbStairs(n-1) + self.climbStairs(n-2)
        return self.dic[n]