leetcode 672. Bulb Switcher II

原题：

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].

这种题还是少放吧，明显是找规律。。。

跟编程又有多少关系呢，，，

int flipLights(int n, int m) {
    if (m * n == 0)
        return 1;
    if (n == 1)
        return 2;
    if (n == 2)
        return 4 - (m % 2);
    if (m == 1)
        return 4;
    if (m == 2)
        return 7;
    return 8;
}