计算年数

Question

我有一个存储日期的String数据。例如：

let dates = ["1-Jan-2015", "1-Feb-2015", "20-Mar-2014", "15-Apr-2014", "12-May-2013", "23-Jun-2012"]

我需要计算当年发生的次数，然后存储它。所以我需要的就是那样的

let years = ["2015" : 2, "2014" : 2, "2013" : 1, "2012" : 1]

我想避免对未来的增长进行硬编码。意思是说，如果我有2020年，我不能多年来难以存储这些值。

所以这里的问题是我不知道我应该如何在概述上做到这一点。另外，如何将String格式转换为日期？

Answer 1

let dates = ["1-Jan-2015", "1-Feb-2015", "20-Mar-2014", "15-Apr-2014", "12-May-2013", "23-Jun-2012"]
// map the last 4 characters of your string
let years = dates.map{String($0.characters.suffix(4))}
// create a dictionary to store tue frequency
var frequencies:[String:Int] = [:]
// loop through the years
for year in years {
    // increase it
    frequencies[year] =  (frequencies[year] ?? 0) + 1
}

let sortedFrequencies = frequencies.sort{ $0.0 < $1.0 }

print(sortedFrequencies)   // [("2012", 1), ("2013", 1), ("2014", 2), ("2015", 2)]\n"

Answer 2

我创建了以下解决方案。使用以下功能，它将在屏幕截图中提供以下结果

 /// This function will return the array as per your requirement
 func getyears(dates: NSArray) -> NSArray
 {
      var year = [String]()
      let newdates = dates
      var countvalue = 0
      for i in dates {

          let x = i.stringByReplacingOccurrencesOfString("-", withString: "")
          let startIndex = x.endIndex.advancedBy(-4)
          let lastFourDigitsOfdate = x.substringFromIndex(startIndex)


          for xm in newdates
          {

              let xy = xm.stringByReplacingOccurrencesOfString("-", withString: "")
              let startIndex1 = xy.endIndex.advancedBy(-4)
              let lastFourDigitsOfdate1 = xy.substringFromIndex(startIndex1)

               if lastFourDigitsOfdate == lastFourDigitsOfdate1
               {
                   countvalue = countvalue + 1
               }
           }
        year.append("\(lastFourDigitsOfdate) : \(countvalue)")

        countvalue = 0
     }


     return getUniqArrayData(year)
 }


 // This function will be required to get an unque array
 func getUniqArrayData<S: SequenceType, E: Hashable where E==S.Generator.Element>(source: S) -> [E] {
      var seen: [E:Bool] = [:]
      return source.filter { seen.updateValue(true, forKey: $0) == nil }
 }


 let dates = ["1-Jan-2015", "1-Feb-2015", "20-Mar-2014", "15-Apr-2014", "12-May-2013", "23-Jun-2012"]


 //Calling the above function
      getyears(dates)

希望这会有所帮助。