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  • 70. Climbing Stairs

    70. Climbing Stairs

    1. 题目

    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

    跳台阶,一次只跳1级或者2级,到最后一级有几种跳法。经典的dp题目。dp[i] 表示到达i阶的时候总共有多少跳法。则:

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

    dp[0] = 0

    dp[1] = 1

    dp[2] = 2

    3. 实现

    class Solution(object):
        def climbStairs(self, n):
            """
            :type n: int
            :rtype: int
            """
            if n == 1 :
                return 1 
            dp = [ 0 ] * n 
            dp[0] = 1
            dp[1] = 2
            
            
            for i in range(2,n):
                dp[i] = dp[i-1] + dp[i-2]
            
            return dp[n-1]
    
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  • 原文地址:https://www.cnblogs.com/bush2582/p/10926300.html
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