70. Climbing Stairs

1. 題目

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.

Example 1:

Input: 2 Output: 2 Explanation: There are two ways to climb to the top. 1. 1 step + 1 step 2. 2 steps

Example 2:

Input: 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

2. 思路

跳臺階，一次只跳1級或者2級，到最后一級有幾種跳法。經典的dp題目。dp[i] 表示到達i階的時候總共有多少跳法。則：

dp[i] = dp[i-1] + dp[i-2]

dp[0] = 0

dp[1] = 1

dp[2] = 2

3. 實現

class Solution(object):def climbStairs(self, n):""":type n: int:rtype: int"""if n == 1 :return 1 dp = [ 0 ] * n dp[0] = 1dp[1] = 2for i in range(2,n):dp[i] = dp[i-1] + dp[i-2]return dp[n-1]

轉載于:https://www.cnblogs.com/bush2582/p/10926300.html

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