70. Climbing Stairs

Today, I solved the climbing staris.

 

Description:

https://leetcode.com/problems/climbing-stairs/description/

 

Solution:

Let's say the example(n = 5).

On the 4th stair, we have only 1 way to get 5th stair.

On the 3rd stair, we have (1 + 1) ways to get 5th stair. 

On the 2nd stair, we have (2 + 1) ways to get 5th stair.

 

In my code, we set (n-1)th stair as "one", and nth stair as "two."

We shift those one and two until we get to 0(start point).

 

(n-1) and (n) is always "1" in any case.