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[Swift]LeetCode539. 最小时间差 | Minimum Time Difference

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Given a list of 24-hour clock time points in "Hour:Minutes" format, find the minimum minutes difference between any two time points in the list.

Example 1:

Input: ["23:59","00:00"]
Output: 1 

Note:

  1. The number of time points in the given list is at least 2 and won't exceed 20000.
  2. The input time is legal and ranges from 00:00 to 23:59.

给定一个 24 小时制（小时:分钟）的时间列表，找出列表中任意两个时间的最小时间差并已分钟数表示。

示例 1：

输入: ["23:59","00:00"]
输出: 1

备注:

　　1.列表中时间数在 2~20000 之间。

 

　　2.

每个时间取值在 00:00~23:59 之间。

Runtime: 104 ms
Memory Usage: 20 MB
 1 class Solution {
 2     func findMinDifference(_ timePoints: [String]) -> Int {
 3         var res:Int = Int.max
 4         var pre:Int = 0
 5         var first:Int = Int.max
 6         var last:Int = Int.min
 7         var mask:[Int] = [Int](repeating:0,count:1440)
 8         for str in timePoints
 9         {
10             var h:Int = Int(str.subString(0, 2))!
11             var m:Int = Int(str.subString(3))!
12             if mask[h * 60 + m] == 1 {return 0}
13             mask[h * 60 + m] = 1
14         }
15         for i in 0..<1440
16         {
17             if mask[i] == 1
18             {
19                 if first != Int.max
20                 {
21                     res = min(res, i - pre)
22                 }
23                 first = min(first, i)
24                 last = max(last, i)
25                 pre = i
26             }
27         }
28         return min(res, 1440 + first - last)
29     }
30 }
31 
32 extension String 
33 {
34     // 截取字符串：指定索引和字符数
35     // - begin: 开始截取处索引
36     // - count: 截取的字符数量
37     func subString(_ begin:Int,_ count:Int) -> String {
38         let start = self.index(self.startIndex, offsetBy: max(0, begin))
39         let end = self.index(self.startIndex, offsetBy:  min(self.count, begin + count))
40         return String(self[start..<end]) 
41     }
42     
43     // 截取字符串：从index到结束处
44     // - Parameter index: 开始索引
45     // - Returns: 子字符串
46     func subString(_ index: Int) -> String {
47         let theIndex = self.index(self.endIndex, offsetBy: index - self.count)
48         return String(self[theIndex..<endIndex])
49     }
50 }

104ms

 1 class Solution {
 2     
 3     private let twentyFourHoursInMinutes = 24*60
 4     
 5     func findMinDifference(_ timePoints: [String]) -> Int {
 6         
 7         // constant space
 8         var minuteBuckets = [Bool](repeating: false, count: twentyFourHoursInMinutes)
 9         
10         // O(N) time
11         for timeString in timePoints {
12             
13             // O(1) time
14             let minutes = convertTimeStringToMinutes(timeString)
15             
16             // if we already contain the `minutes`, that means the time difference will be 0
17             if minuteBuckets[minutes] {
18                 return 0
19             }
20             
21             minuteBuckets[minutes] = true
22         }
23         
24         var minDifference = twentyFourHoursInMinutes
25         var firstMinute = 0
26         var lastMinute = -1
27         
28         // O(1) time
29         for minute in 0..<minuteBuckets.count {
30             guard minuteBuckets[minute] else {
31                 continue
32             }
33             
34             if lastMinute == -1 {
35                 firstMinute = minute
36             } else {
37                 minDifference = min(minDifference, minute - lastMinute)
38             }
39             
40             lastMinute = minute
41         }
42         
43         minDifference = min(minDifference, firstMinute + (twentyFourHoursInMinutes - lastMinute))
44         
45         return minDifference
46     }
47     
48     func convertTimeStringToMinutes(_ timeString: String) -> Int {
49         let hoursAndMinutes = timeString.split(separator: ":")
50         guard let hours = Int(hoursAndMinutes[0]), let minutes = Int(hoursAndMinutes[1]) else {
51             assertionFailure("...")
52             return 0
53         }
54         return (hours * 60) + minutes
55     }
56 }

108ms

 1 class Solution {
 2     func findMinDifference(_ timePoints: [String]) -> Int {
 3         let timePointsSet = Set<String>(timePoints)
 4         
 5         if (timePoints.count !=  timePointsSet.count) {
 6             return 0
 7         }
 8 
 9         let timePoints = [String](timePointsSet).sorted()
10         
11         
12         var minResult = timeDifference(timePoints[0], timePoints[timePoints.count - 1])
13         
14         let maxIndex = timePoints.count - 2
15         for index in 0...maxIndex {
16             minResult = min(minResult, timeDifference(timePoints[index], timePoints[index+1]))
17         }
18      
19         return minResult
20     }
21     
22     private func timeDifference(_ time0 : String, _ time1 : String) -> Int {
23         var minutes0 = minutesFromTimeString(time0)
24         var minutes1 = minutesFromTimeString(time1)
25         
26         if (minutes0 > minutes1) {
27             swap(&minutes0, &minutes1)
28         }
29 
30         return min(minutes1 - minutes0, minutes0 + 24*60 - minutes1)
31     }
32     
33     private func minutesFromTimeString(_ timeStr : String) -> Int {
34         let foundIndex = timeStr.firstIndex(of: ":") ?? timeStr.startIndex
35         let hourStr = timeStr[..<foundIndex]
36         let nextIndex = timeStr.index(after: foundIndex)
37         let minuteStr = timeStr[nextIndex...]
38         
39         let hour = Int(hourStr)!
40         let minute = Int(minuteStr)!
41 
42         return hour * 60 + minute
43     }
44 }

148ms

 1 class Solution {
 2     func getMinute(_ timePoint: String) -> Int {
 3         var times = timePoint.split(separator: ":")
 4         return Int(times[0])!*60 + Int(times[1])!
 5     }
 6     
 7     func findMinDifference(_ timePoints: [String]) -> Int {
 8         if timePoints.count <= 1 {
 9             return 0
10         }
11 
12         var points: [Int] = timePoints.map { getMinute($0) }
13         points.sort()
14         
15         var minn = 24*60 + points.first! - points.last!
16         
17         for i in 1..<points.count {
18             minn = min(minn, points[i]-points[i-1])
19         }
20         return minn
21     }
22 }

156ms

 1 struct Time {
 2     let hours: Int
 3     let minutes: Int
 4 }
 5 
 6 extension Time: Comparable {
 7     static func <(lhs: Time, rhs: Time) -> Bool {
 8         return lhs.hours < rhs.hours || (lhs.hours == rhs.hours && lhs.minutes < rhs.minutes)
 9     }
10 }
11 
12 class Solution {
13     func findMinDifference(_ timePoints: [String]) -> Int {
14         
15         let timePoints = timePoints
16             .map { convertToTime($0) }
17             .sorted()
18         
19         var minDifference = Int.max
20         for i in 1..<timePoints.count {
21             minDifference = min(
22                 minDifference,
23                 calculateDifference(timePoints[i-1], timePoints[i]))
24         }
25         minDifference = min(
26                 minDifference,
27                 calculateDifference(timePoints[0], timePoints[timePoints.count-1]))
28         
29         return minDifference
30     }
31     
32     func calculateDifference(_ time1: Time, _ time2: Time) -> Int {
33 
34         return min(
35             calculateDifference_helper(time1, time2),
36             calculateDifference_helper(time2, Time(hours: time1.hours+24, minutes: time1.minutes))
37         )
38     }
39     
40     func calculateDifference_helper(_ time1: Time, _ time2: Time) -> Int {
41         return ((time2.hours - time1.hours) * 60) + (time2.minutes - time1.minutes)
42     }
43     
44     func convertToTime(_ timeString: String) -> Time {
45         let timeUnits = timeString.split(separator: ":")
46         guard let hours = Int(timeUnits[0]), let minutes = Int(timeUnits[1]) else {
47             assertionFailure("...")
48             return Time(hours: 0, minutes: 0)
49         }
50         return Time(hours: hours, minutes: minutes)
51     }
52 }

164ms

 1 typealias Time = (hours: Int, minutes: Int)
 2 
 3 class Solution {
 4     func findMinDifference(_ timePoints: [String]) -> Int {
 5         
 6         var buckets = [[Int]](repeating: [Int](repeating: 0, count: 60), count: 24)
 7         
 8         for timeString in timePoints {
 9             let time = convertTimeString(timeString)
10             buckets[time.hours][time.minutes] += 1
11         }
12         
13         var times: [Time] = []
14         for hour in 0..<buckets.count  {
15             for minutes in 0..<buckets[hour].count {
16                 for _ in 0..<buckets[hour][minutes] {
17                     times.append(Time(hour,minutes))
18                 }
19             }
20         }
21         
22         var minDifference = Int.max
23         for i in 1..<times.count {
24             let difference = timeDifference(times[i-1], times[i])
25             minDifference = min(minDifference, difference)
26         }
27         minDifference = min(minDifference, timeDifference(times[0], times[times.count-1]))
28         
29         return minDifference
30     }
31     
32     func timeDifference(_ time1: Time, _ time2: Time) -> Int {
33         let diff1 = timeDifference_helper(time1, time2)
34         let diff2 = timeDifference_helper(time2, (time1.hours+24, time1.minutes))
35         return min(diff1, diff2)
36     }
37     
38     func timeDifference_helper(_ time1: Time, _ time2: Time) -> Int {
39         return (time2.hours - time1.hours)*60 + (time2.minutes - time1.minutes)
40     }
41     
42     func convertTimeString(_ timeString: String) -> Time {
43         let timeStringSplit = timeString.split(separator: ":")
44         guard let hours = Int(timeStringSplit[0]), let minutes = Int(timeStringSplit[1]) else {
45             return (0,0)
46         }
47         return (hours,minutes)
48     }
49 }

188ms

 1 class Solution {
 2 func getTime(_ time: String) -> Int {
 3     let array = time.split(separator: ":")
 4     guard array.count == 2 else {
 5         return 0
 6     }
 7     
 8     let hours = Int(array[0])!
 9     let minute = Int(array[1])!
10     
11     return hours * 60 + minute
12 }
13 
14 func findMinDifference(_ timePoints: [String]) -> Int {
15     let sorted = timePoints.sorted()
16     
17     var minDiff = Int.max
18     let n = timePoints.count
19     
20     for i in 0..<n {
21         var diff = getTime(sorted[(i - 1 + n) % n]) - getTime(sorted[i])
22         diff = abs(diff)
23         diff = min(diff, 60 * 24 - diff)
24         minDiff = min(diff, minDiff)
25     }
26     
27     return minDiff
28   }
29 }

208ms

 1 class Solution {
 2     
 3     func findMinDifference(_ timePoints: [String]) -> Int {
 4         var sorted = timePoints.sorted()
 5         var previous: String?
 6         var diff = Int.max
 7         for point in sorted {
 8             guard let prev = previous else {
 9                 if let last = sorted.last {
10                     let curDiff = timeDiff(point, last)
11                     diff = min(diff, curDiff, 24 * 60 - curDiff)
12                 }
13                 previous = point
14                 continue
15             }
16             let curDiff = timeDiff(point, prev)
17             diff = min(diff, curDiff, 24 * 60 - curDiff)
18             previous = point
19         }
20         return diff
21     }
22     
23     func timeDiff(_ a: String, _ b: String) -> Int {
24         return abs(absTime(string: a) - absTime(string: b))
25     }
26     
27     func absTime(string: String) -> Int {
28         let split = string.split(separator: ":").map { Int($0)! }
29         return split[0] * 60 + split[1]
30     }       
31 }

 

 

posted @ 2019-02-20 19:27  为敢技术  阅读(402)  评论(0)  编辑  收藏  举报