"""
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
"""
class ClimbingStairs:
    def climbStairs(self, n: int) -> int:
        if n == 1:
            return 1
        dp = [0 for _ in range(n)]
        dp[0], dp[1] = 1, 2
        for i in range(2, n):
            dp[i] = dp[i - 1] + dp[i - 2]
        return dp[-1]
