70. Climbing Stairs

class Solution:
    def climbStairs(self, n: int) -> int:
        if n == 1:
            return 1
        
        dp = [1, 2]
        
        for i in range(2, n):
            num_ways = dp[i-1] + dp[i-2]
            dp.append(num_ways)
        
        return dp[-1]

• simple dynamic-programming.
• you can reach the next step by either going from one or two steps below, so the number of ways to reach step n is the number of ways to reach step n-1 and the number of ways to reach step n-2.

Categories:: dynamic-programming