70. Climbing Stairs

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: 2Output:  2Explanation:  There are two ways to climb to the top.1. 1 step + 1 step2. 2 steps

Example 2:

Input: 3Output:  3Explanation:  There are three ways to climb to the top.1. 1 step + 1 step + 1 step2. 1 step + 2 steps3. 2 steps + 1 step

动态规划：dp[n]=dp[n-1]+dp[n-2]，弄得此题类似斐波那契数列。。。

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