[勇者闯LeetCode] 70. Climbing Stairs

[勇者闯LeetCode] 70. Climbing Stairs

Description

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.

Information

Tags: Dynamic Programming

Difficulty: Easy

Solution

实质上是Fibonacci Number：

Fib(n)=Fib(n−1)+Fib(n−2),Fib(1)=1,Fib(2)=2，

即爬到n阶的方法数等于爬到n-1阶的方法数和爬到n-2阶的方法数之和，爬到1阶的方法数是1，爬到2阶的方法数是2。

class Solution(object):
def climbStairs(self, n):
"""
:type n: int
:rtype: int
"""
prev, cur = 0, 1
for i in range(n):
prev, cur = cur, cur + prev
return cur