leetcode-easy-dynamic-70 Climbing Stairs

mycode  65%

class Solution(object):
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n == 1:
            return 1
        if n == 2:
            return 2
        i = 3
        dic = {1:1,2:2}
        while i < n+1:
            dic[i] = dic[i-2] + dic[i-1]
            i += 1
        return dic[n]

下面这个会超时。。。

class Solution(object):
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n == 1:
            return 1
        if n == 2:
            return 2
        return self.climbStairs(n-1) + self.climbStairs(n-2)

参考

class Solution(object):
    def climbStairs(self, n):
        a, b = 1, 1
        for i in range(n):
            a, b = b, a + b
        return a