[Swift]LeetCode672. 灯泡开关 Ⅱ | Bulb Switcher II

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There is a room with n lights which are turned on initially and 4 buttons on the wall. After performing exactly munknown 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].

---

现有一个房间，墙上挂有 n 只已经打开的灯泡和 4 个按钮。在进行了 m 次未知操做后，你须要返回这 n 只灯泡可能有多少种不一样的状态。

假设这 n 只灯泡被编号为 [1, 2, 3 ..., n]，这 4 个按钮的功能以下：

1. 将全部灯泡的状态反转（即开变为关，关变为开）
2. 将编号为偶数的灯泡的状态反转
3. 将编号为奇数的灯泡的状态反转
4. 将编号为 3k+1 的灯泡的状态反转（k = 0, 1, 2, ...)

示例 1:

输入: n = 1, m = 1.
输出: 2
说明: 状态为: [开], [关]

示例 2:

输入: n = 2, m = 1.
输出: 3
说明: 状态为: [开, 关], [关, 开], [关, 关]

示例 3:

输入: n = 3, m = 1.
输出: 4
说明: 状态为: [关, 开, 关], [开, 关, 开], [关, 关, 关], [关, 开, 开].

注意： n 和 m 都属于 [0, 1000].

---

Runtime: 4 ms

Memory Usage: 18.9 MB

1 class Solution {
2     func flipLights(_ n: Int, _ m: Int) -> Int {
3         var n = min(n, 3)
4         return min(1 << n, 1 + m * n)
5     }
6 }

---

4ms

 1 class Solution {
 2     struct State: Hashable, OptionSet {
 3         let rawValue: Int
 4 
 5         static let oddSensitive = State(rawValue: 1)
 6         static let evenInsensitive = State(rawValue: 2)
 7         static let oddInsensitive = State(rawValue: 4)
 8         static let evenSensitive = State(rawValue: 8)
 9         
10         static let odd: State = [.oddSensitive, .oddInsensitive]
11         static let even: State = [.evenSensitive, .evenInsensitive]
12         static let sensitive: State = [.evenSensitive, .oddSensitive]
13         
14         static let all: State = [.oddSensitive, .oddInsensitive, .evenSensitive, .evenInsensitive]
15     }
16     
17     func flipLights(_ n: Int, _ m: Int) -> Int {
18         let mask = State(rawValue: 1 << min(n, 4) - 1)
19         let permittedCount = Set<Int>(0...4).filter { $0 <= m && ($0 % 2) == (m % 2) }
20 
21         var states = Set<State>()
22         
23         for i in 0..<16 {
24             var count = 0, state = State.all
25             if (i & 1) != 0 {
26                 state.formSymmetricDifference(.all)
27                 count += 1
28             }
29             if (i & 2) != 0 {
30                 state.formSymmetricDifference(.even)
31                 count += 1
32             }
33             if (i & 4) != 0 {
34                 state.formSymmetricDifference(.odd)
35                 count += 1
36             }
37             if (i & 8) != 0 {
38                 state.formSymmetricDifference(.sensitive)
39                 count += 1
40             }
41             
42             if permittedCount.contains(count) {
43                 states.insert(state.intersection(mask))
44             }
45         }
46         
47         return states.count
48     }
49 }