排序面试题

已知有很多会议,如果这些会议的时间有重叠，则将他们合并.
例如，有一个会议的时间为下午3点到下午5点，另外一个会议的时间为下午4点到6点，那么合并之后的会议时间为下午3点到6点。

    func mergeSort(_ arr : [MeetingTime]) -> [MeetingTime]{
        var arr = arr
        guard arr.count > 0 else{
            return []
        }
        arr.sort { (time1, time2) -> Bool in
            if time1.start != time2.start{
                return time1.start < time2.start
            }else{
                return time1.end < time2.end
            }
        }
        
        for item in arr{
            print("\(item.start):\(item.end)")
        }
        
        //定义一个数组 用来装合并后的值
        var res = [MeetingTime]()
        res.append(arr[0])
        for i in 1...arr.count - 1{
            let current = arr[i]
            let last = res.last!
            if current.start > last.end{
                res.append(current)
            }else{
                last.end = max(last.end,current.end)
            }
        }
        return res
    }
    class MeetingTime{
        var start : Int
        var end : Int
        public init(_ start : Int,_ end : Int){
            self.start = start
            self.end = end
        }
    }

        var arr = [MeetingTime]()
        
        let time1 = MeetingTime(0, 1)
        let time2 = MeetingTime(1, 2)
        let time3 = MeetingTime(9, 10)
        let time4 = MeetingTime(4, 6)
        let time5 = MeetingTime(5, 8)
        let time6 = MeetingTime(1, 2)
        let time7 = MeetingTime(18, 20)
        let time8 = MeetingTime(22, 21)
        arr.append(time1)
        arr.append(time2)
        arr.append(time3)
        arr.append(time4)
        arr.append(time5)
        arr.append(time6)
        arr.append(time7)
        arr.append(time8)
        let res = mergeSort(arr)
        print("-------归并结果--------")
        for item in res{
            print("\(item.start):\(item.end)")
        }

打印结果：
0:1
1:2
1:2
4:6
5:8
9:10
18:20
22:21
-------归并结果--------
0:2
4:8
9:10
18:20
22:21