[Swift]LeetCode401. 二进制手表 | Binary Watch

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A binary watch has 4 LEDs on the top which represent the hours (0-11), and the 6 LEDs on the bottom represent the minutes (0-59).

Each LED represents a zero or one, with the least significant bit on the right.

For example, the above binary watch reads "3:25".

Given a non-negative integer n which represents the number of LEDs that are currently on, return all possible times the watch could represent.

Example:

Input: n = 1
Return: ["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]

Note:

• The order of output does not matter.
• The hour must not contain a leading zero, for example "01:00" is not valid, it should be "1:00".
• The minute must be consist of two digits and may contain a leading zero, for example "10:2" is not valid, it should be "10:02".

---

 二进制手表顶部有 4 个 LED 代表小时（0-11），底部的 6 个 LED 代表分钟（0-59）。

每个 LED 代表一个 0 或 1，最低位在右侧。

例如，上面的二进制手表读取 “3:25”。

给定一个非负整数 n 代表当前 LED 亮着的数量，返回所有可能的时间。

案例:

输入: n = 1
返回: ["1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"]

注意事项:

• 输出的顺序没有要求。
• 小时不会以零开头，比如 “01:00” 是不允许的，应为 “1:00”。
• 分钟必须由两位数组成，可能会以零开头，比如 “10:2” 是无效的，应为 “10:02”。

---

class Solution {
    func readBinaryWatch(_ num: Int) -> [String] {
        var times:[String] = [String]()   
        //轮询遍历
        for h in 0..<12
        {
            //将常量转换为变量
            var hour:Int = h
            for m in 0..<60
            {
                //将常量转换为变量
                var minute:Int = m
                var number:Int = hour*64 + minute
                if number.bitCount() == num
                {
                    //minute不足2位前面补0的写法：%02d
                    var str = String(format: "%d:%02d", arguments:[hour,minute]) 
                    times.append(str)
                }
            }           
        }
        return times
    }   
}
//Int扩展代码
extension Int
{
    mutating func bitCount() -> Int
    {
        self = self - ((self >> 1) & 0x55555555);
        self = (self & 0x33333333) + ((self >> 2) & 0x33333333);
        self = (self + (self >> 4)) & 0x0f0f0f0f;
        self = self + (self >> 8);
        self = self + (self >> 16);
        return self & 0x3f;        
    }
}

---

8ms

class Solution {
    func readBinaryWatch(_ num: Int) -> [String] {
       
        let leds = [1, 2, 4, 8, 1, 2, 4, 8, 16, 32]
        var result = [String]()
        readBinaryWatch(leds, leds.count, 0, (leds.count - num), 0, 0, &result) 
        return result
    } 
    
    func readBinaryWatch(_ leds: [Int], _ ledsCount: Int, _ left: Int, _ right: Int, _ hours: Int, _ minutes: Int, _ result: inout [String]) {
        if hours > 11 || minutes > 59 { return }
        if right >= leds.count {
            result.append(String(format: "%d:%02d", hours, minutes)) 
            return 
        }
        
        for index in left...right {
            var currentHours = hours
            var currentMinutes = minutes
            
            let value = leds[index]
            if index >= 4 { currentMinutes += value } 
            else { currentHours += value } 
            
            readBinaryWatch(leds, ledsCount, index + 1, right + 1, currentHours, currentMinutes, &result)  
        }
    }
    
}

---

12ms

class Solution {
    let hourArray = [
        [0],
        [1, 2, 4, 8],
        [3, 5, 6, 9, 10],
        [7, 11]
    ]
    let minArray = [
        [0],
        [1, 2, 4, 8, 16, 32],
        [3, 5, 6, 9, 10, 12, 17, 18, 20, 24, 33, 34, 36, 40, 48],
        [7, 11, 13, 14, 19, 21, 22, 25, 26, 28, 35, 37, 38, 41, 42, 44, 49, 50, 52, 56],
        [15, 23, 27, 29, 30, 39, 43, 45, 46, 51, 53, 54, 57, 58],
        [31, 47, 55, 59]
    ]
    func readBinaryWatch(_ num: Int) -> [String] {
        var result = [String]()
        
        for hNum in 0...min(3, num) {
            let mNum = num - hNum
            if mNum < minArray.count {
                for h in hourArray[hNum] {
                    for m in minArray[mNum] {
                        result.append("\(h):\(String(format: "%02d", m))")
                    }
                }
            }
        }
        return result
    }
}

---

20ms

class Solution {
    func readBinaryWatch(_ num: Int) -> [String] {
        var times: [String] = []
        let maxClock = num == 1 ? 8 : 11
        let maxMinute = num == 1 ? 32 : 59
        for clock in 0...maxClock {
            for minute in 0...maxMinute {
                if bitCount(clock) + bitCount(minute) == num {
                    let time = String(format: "%d:%02d", clock, minute)
                    times.append(time)
                }
            }
        }
        
        return times
    }
    
    func bitCount(_ num: Int) -> Int {
        var result = 0
        var num2 = num
        while num2 > 0 {
            result += num2 & 1
            num2 >>= 1
        }
        
        return result
    }
}

---

28ms

class Solution {
    func readBinaryWatch(_ num: Int) -> [String] {
        var res = [String]()

        func bitCount(_ num: Int) -> Int {
            var count = 0
            var num = num
            while num > 0 {
                count += num & 1
                num >>= 1
            }
            return count
        }

        for h in 0...11 {
            for m in 0...59 {
                if bitCount(h) + bitCount(m) == num {
                    res.append(String(format: "%d:%02d", h, m))
                }
            }
        }

        return res
    }
}

---

48ms

class Solution {
    func readBinaryWatch(_ num: Int) -> [String] {
        var ret: [String] = []
        
        for i in 0...11 {
            for j in 0...59 {
                let hourBinary = String(i, radix: 2).filter { $0 == "1" }
                let minuteBinary = String(j, radix: 2).filter { $0 == "1" }
                
                if hourBinary.count + minuteBinary.count == num {
                    ret.append(String(format: "%d:%02d", i, j))
                }
            }
        }
        
        return ret
    }
}

---

48ms

class Solution {
    func readBinaryWatch(_ num: Int) -> [String] {
        var res = [String]()

        func findLEDs(_ h: Int, _ m: Int) -> Int {
            let hc = Array(String(h, radix: 2)).filter { $0 == "1" }.count
            let mc = Array(String(m, radix: 2)).filter { $0 == "1" }.count
            return hc + mc
        }

        for h in 0...11 {
            for m in 0...59 {
                if findLEDs(h, m) == num {
                    res.append(String(format: "%d:%02d", h, m))
                }
            }
        }

        return res
    }
}

---

52ms

class Solution {
    func readBinaryWatch(_ num: Int) -> [String] {
    var result = [String]()
    
    func findLEDs(_ h: Int, _ m: Int) -> Int {
        let hc = Array(String(h, radix: 2).characters).filter { $0 == "1" }.count
        let mc = Array(String(m, radix: 2).characters).filter { $0 == "1" }.count
        return hc + mc
    }
    for h in 0...11 {
        for m in 0...59 {
            if findLEDs(h, m) == num {
                result.append(String(format: "%d:%02d", h, m))
            }
        }
    }
    return result
    }
}