如何确定多个（n）日期时间范围何时相互重叠

Question

我正在寻找一个可以调用的函数，该函数可以告诉我所有（p）个人同时可用的日期时间范围。 请为我提供Objective-c或Swift语言。

p1: start: "2016-01-01 12:00", end: "2016-05-01 03:00"
p2: start: "2016-01-01 03:00", end: "2016-05-01 03:00"
p3: start: "2016-01-01 03:00", end: "2016-04-30 13:31"

在以上示例中，答案应为：

start: 2016-04-30 12:00, end: 2016-04-30 13:31

Answer 1

将日期对转换为NSDateInterval对象，并采用它们的交集：

https://developer.apple.com/documentation/foundation/nsdateinterval/1641645-intersectionwithdateinterval

该文档甚至提供了一个相当不错的图表：

Answer 2

您需要执行以下步骤：

1. 将您的日期字符串转换为Date对象。
2. 使用开始和结束日期对象创建DateIntervals。
3. 遍历区间并检查交叉点。

这是我可以快速提出的快速代码：

func answer()  {
    let dateFormat = "yyyy-MM-dd HH:mm Z"
    // Date ranges
    let times = [["start": "2016-01-01 12:00 +0000", "end": "2016-05-01 03:00 +0000"],
                 ["start": "2016-01-01 03:00 +0000", "end": "2016-05-01 03:00 +0000"],
                 ["start": "2016-01-01 03:00 +0000", "end": "2016-04-30 13:31 +0000"]]

    var intervals = [DateInterval]()
    // Loop through date ranges to convert them to date intervals
    for item in times {
        if let start = convertStringToDate(string: item["start"]!, withFormat: dateFormat),
            let end = convertStringToDate(string: item["end"]!, withFormat: dateFormat) {
            intervals.append(DateInterval(start: start, end: end))
        }
    }

    // Check for intersection
    let intersection = intersect(intervals: intervals)
    print(intersection)
}

// Converts the string to date with given format
func convertStringToDate(string: String, withFormat format: String)  -> Date? {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = format
    return dateFormatter.date(from: string)
}

// Cehck for intersection among the intervals in the given array and return
    // the interval if found.
    func intersect(intervals: [DateInterval]) -> DateInterval? {
        // Algorithm:
        // We will compare first two intervals.
        // If an intersection is found, we will save the resultant interval
        // and compare it with the next interval in the array.
        // If no intersection is found at any iteration
        // it means the intervals in the array are disjoint. Break the loop and return nil
        // Otherwise return the last intersection.

        var previous = intervals.first
        for (index, element) in intervals.enumerated() {
            if index == 0 {
                continue
            }

            previous = previous?.intersection(with: element)

            if previous == nil {
                break
            }
        }

        return previous
    }

注意：请通过几个示例进行测试。 我测试了上述日期范围及其工作正常。