LeetCode - Climbing Stairs

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

 

Constraints:

• 1 <= n <= 45

 

My Solution:

class Solution:
    def climbStairs(self, n: int) -> int:
        if n == 1:
            return 1
        elif n == 2:
            return 2
        
        n1 = 1
        n2 = 2
        for _ in range(3, n + 1):
            result = n1 + n2
            n1 = n2
            n2 = result
        
        return result