Question
You are climbing a stair case. It takes n steps to reach to the top.
Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
Note: Given n will be a positive integer.
你正在爬楼梯,它需要n步才能到达顶端。每次你既可以走一步也可以走两步。现在问有多少种方法爬到顶端。(n是正整数)
Example
None
Solution
动态规划解。定义dp[i]:爬到第i层的方法数。递推式dp[i] = dp[i - 1] + dp[i - 2],即爬一步的方法数加上爬两步的次数就是dp[i]的次数
class Solution(object): def climbStairs(self, n): """ :type n: int :rtype: int """ ways_climb = [0] * n for index in range(n): if index == 0: ways_climb[index] += 1 elif index == 1: ways_climb[index] = ways_climb[index - 1] + 1 else: ways_climb[index] = ways_climb[index - 1] + ways_climb[index - 2] return ways_climb[-1]