剑指offer04跳台阶

题目描述
一只青蛙一次可以跳上1级台阶，也可以跳上2级。求该青蛙跳上一个n级的台阶总共有多少种跳法（先后次序不同算不同的结果）。

# -*- coding:utf-8 -*-
class Solution:
    def jumpFloor(self, number):
        res = 0
        # write code here
        if (number == 1):
            res = 1
        elif (number == 2):
            res = 2
        else:
            res = self.jumpFloor(number-1)+self.jumpFloor(number-2)
        return res
            

出现溢出问题同第三题斐波那契数列

修改后

# -*- coding:utf-8 -*-
class Solution:
    def jumpFloor(self, number):
        res = 0
        ppnum = 1
        pnum = 2
        # write code here
        if (number == 1):
            res = 1
        elif (number == 2):
            res = 2
        else:
            for i in range(3,number+1):
                res = pnum + ppnum
                ppnum = pnum
                pnum = res
        return res