# 672. Bulb Switcher II 灯泡开关 Ⅱ

@TOC

## # 题目描述

There is a room with n lights which are turned on initially and 4 buttons on the wall. After performing exactly m unknown operations towards buttons, you need to return how many different kinds of status of the n lights could be.

Suppose n lights are labeled as number [1, 2, 3 ..., n], function of these 4 buttons are given below:

1. Flip all the lights.
2. Flip lights with even numbers.
3. Flip lights with odd numbers.
4. Flip lights with (3k + 1) numbers, k = 0, 1, 2, ...

Example 1:

``````    Input: n = 1, m = 1.
Output: 2
Explanation: Status can be: [on], [off]
``````

Example 2:

``````    Input: n = 2, m = 1.
Output: 3
Explanation: Status can be: [on, off], [off, on], [off, off]
``````

Example 3:

``````    Input: n = 3, m = 1.
Output: 4
Explanation: Status can be: [off, on, off], [on, off, on], [off, off, off], [off, on, on].
``````

Note: n and m both fit in range [0, 1000].

## # 解题方法

``````class Solution:
def flipLights(self, n, m):
"""
:type n: int
:type m: int
:rtype: int
"""
if m == 0:
return 1
if n >= 3:
return 4 if m == 1 else 7 if m == 2 else 8
if n == 2:
return 3 if m == 1 else 4
if n == 1:
return 2
``````

2018 年 3 月 5 日