[leetcode] 70. Climbing Stairs

题目

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

思路

动态规划，当前次数等于前一台阶次数+前前台阶次数。

代码

python版本：

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