672. Bulb Switcher II

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].

Rust Solution

struct Solution;

impl Solution {
    fn flip_lights(n: i32, m: i32) -> i32 {
        let n = n.min(3);
        if m == 0 || n == 0 {
            return 1;
        }
        if n == 1 {
            return 2;
        }
        if n == 2 {
            return if m == 1 { 3 } else { 4 };
        }
        if m == 1 {
            return 4;
        }
        if m == 2 {
            7
        } else {
            8
        }
    }
}

#[test]
fn test() {
    let n = 1;
    let m = 1;
    let res = 2;
    assert_eq!(Solution::flip_lights(n, m), res);
    let n = 2;
    let m = 1;
    let res = 3;
    assert_eq!(Solution::flip_lights(n, m), res);
    let n = 3;
    let m = 1;
    let res = 4;
    assert_eq!(Solution::flip_lights(n, m), res);
}

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