Bulb Switcher

题目
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:

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

答案

class Solution {
    public int flipLights(int n, int m) {
        if(m == 0) return 1;
        if(n == 1) return 2;
        if(n == 2) {
            if(m == 1) return 3;
            if(m >= 2) return 4;
        }
        if(n >= 3) {
            if(m == 1) return 4;
            if(m == 2) return 7;
            if(m >= 3) return 8;
        }
        return 0;
    }
}