BinarySearch 0010 A Flight of Stairs

Problem statement

https://binarysearch.com/problems/A-Flight-of-Stairs/

Solution

Almost the same as leetcode Leetcode 0070. Climbing Stairs

Complexity

It is O(n) for time and O(1) for space.

Code

class Solution:
    def solve(self, n):
        dp, M = (1, 1), 10**9 + 7
        for i in range(n-1):
            dp = (dp[1] % M, (dp[0] + dp[1]) % M)
        return dp[1]