变态跳台阶 牛客网 剑指Offer

变态跳台阶 牛客网 剑指Offer

• 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……它也可以跳上n级。求该青蛙跳上一个n级的台阶总共有多少种跳法。

class Solution:
    def jumpFloorII(self, number):
        return 2**(number - 1)
    
    def jumpFloorII2(self, number):
        return pow(2,number - 1)
    
    def jumpFloorI3(self, number):
        return self.mypow(2,number - 1)
    
    def mypow(self,x,n):
        if n == 0:
            return 1
        if n%2 == 0:
            return self.mypow(x*x,n/2)
        else:
            return self.mypow(x*x,n/2)*x

    #run:27ms memory:5680k
    def jumpFloorII4(self, number):
        if number <= 0:
            return 0
        if number == 1:
            return 1
        if number == 2:
            return 2
        i = 3
        lt = []
        lt.append(1)
        lt.append(2)
        while i<=number:
            ret = 0
            for j in range(len(lt)):
                ret = ret + lt[j]
            ret +=1
            lt.append(ret)
            i +=1
        return lt[number-1]