剑指9：变态跳台阶

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……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 {
public:
    int jumpFloorII(int number) {
        int jumpFlo=1;
        while(--number)
        {
            jumpFlo*=2;
        }
        return jumpFlo;
    }
};

 

# -*- coding:utf-8 -*-
class Solution:
    def jumpFloorII(self, number):
        # write code here
        
        return 1<<(number-1)

 

public class Solution {
    public int JumpFloorII(int target) {
        if (target<=0){
            return -1;
        }else if (target==1){
            return 1;
        }else {
            return 2*JumpFloorII(target-1);
        }
    }
}