文件的每一行用于构造一个以股票代码作为键的映射条目，以及一个整数列表作为值。结构的类型是Map [String，List [Int]]。 目前，我的系统可以在列表中搜索单个条目，并为其显示不同的结果。我怎么比较列表中的2？ 我如何比较此列表中的2个项目？请在下面找到我目前拥有的代码，我很欣赏我应该为您提供代码供您评估，但我不知道如何开始这个。任何和所有的帮助表示赞赏。
/**
* Created by Andre on 10/11/2016.
*/
import scala.io.Source
import scala.io.StdIn.readInt
import scala.io.StdIn.readLine
import scala.collection.immutable.ListMap
import scala.util.Try
object StockMarket extends App {
// *******************************************************************************************************************
// application logic
// read data from file
val mapdata = readFile("data.txt")
// print data to check it's been read in correctly
//println(mapdata)
// define menu options as a Map of actions
// for each menu item:
// key is an Int, the value that will be read from the input
// value is a function () => Boolean, i.e. no params and returns Boolean
val actionMap = Map[Int, () => Boolean](1 -> handleOne, 2 -> handleTwo, 3 -> handleThree, 4 -> handleFour, 5 -> handleFive, 6 -> handleSix, 8-> handleEight)
// loop to read input and invoke menu option
// uses function readOption to show menu and read input
// uses function menu to invoke menu action
// will terminate if menu returns false
var opt = 0
do {
opt = readOption
} while (menu(opt))
// *******************************************************************************************************************
// FUNCTIONS FOR MENU
// shows menu and reads input
def readOption: Int = {
println(
"""|Please select one of the following:
| 1 - show All stock levels
| 2 - Show Selected Stock Level
| 3 - Show Highest Stock Level
| 4 - Show Lowest Stock Level
| 5 - Show Current Stock Level
| 6 - Show Average Stock Level
| 8 - quit""".stripMargin)
readInt()
}
// invokes selected menu option
// finds corresponding function to invoke in action map using get
// pattern matching used as get returns an Option
def menu(option: Int): Boolean = {
actionMap.get(option) match {
case Some(f) => f()
case None =>
println("Sorry, that command is not recognized")
true
}
}
// handlers for menu options
def handleOne(): Boolean = {
mnuShowPoints(currentPoints)
true
}
def handleTwo(): Boolean = {
mnuShowPointsForStock(allStockLevel)
true
}
def handleThree(): Boolean = {
mnuShowSingleDataStock(highestStockLevel)
true
}
def handleFour(): Boolean = {
mnuShowSingleDataStock(lowestStockLevel)
true
}
def handleFive(): Boolean = {
mnuShowSingleDataStock(currentStockLevel)
true
}
def handleSix(): Boolean = {
mnuShowSingleDataStock(averageStockLevel)
true
}
def handleEight(): Boolean = {
println("selected quit") // returns false so loop terminates
false
}
// *******************************************************************************************************************
// UTILITY FUNCTIONS
//GETS THE DATA FROM THE DATA.TXT
def readFile(filename: String): Map[String, List[Int]] = {
processInput(Source.fromFile(filename).getLines)
}
def processInput(lines: Iterator[String]): Map[String, List[Int]] = {
Try {
lines.foldLeft(Map[String, List[Int]]()) { (acc, line) =>
val splitline = line.split(",").map(_.trim).toList
acc.updated(splitline.head, splitline.tail.map(_.toInt))
}
}.getOrElse {
println("Sorry, an exception happened.")
Map()
}
}
// *******************************************************************************************************************
// FUNCTIONS THAT INVOKE ACTION AND INTERACT WITH USER
// each of these functions accepts user input if required for an operation,
// invokes the relevant operation function and displays the results
def mnuShowPoints(f:() => Map[String,List[Int]]) = {
f() foreach {case (x,y) => println(s"$x: $y")}
}
//Returns a list value
def mnuShowPointsForStock(f: (String) => (String,List[Int])) = {
print("Stock > ")
val data = f(readLine)
println(s"${data._1}: ${data._2}")
}
// Returns a single result, not a list
def mnuShowSingleDataStock(f: (String) => (String,Int)) = {
print("Stock > ")
val data = f(readLine)
println(s"${data._1}: ${data._2}")
}
//functionality to find the last tail element, the "Current" stock price
def findLast(list:List[Int]) = list.last
//Function to find the average
def average(list:List[Int]): Double = list.sum.toDouble / list.size
// *******************************************************************************************************************
// OPERATION FUNCTIONS
// each of these performs the required operation on the data and returns
// the results to be displayed - does not interact with user
def currentPoints():Map[String,List[Int]] = {
// sort map by value in descending order -
ListMap(mapdata.toSeq.sortWith(_._1 < _._1):_*)
}
def allStockLevel(team: String): (String, List[Int]) =
(team, mapdata.get(team).getOrElse(List.empty))
//Shows Highest Stock
def highestStockLevel(stock: String): (String, Int) =
(stock, mapdata.get(stock).map(_.max).getOrElse(0))
//Shows the Lowest Stock
def lowestStockLevel(stock: String): (String, Int) =
(stock, mapdata.get(stock).map(_.min).getOrElse(0))
//Show last element in the list, most current
def currentStockLevel (stock: String): (String, Int) = {
(stock, mapdata.get (stock).map(findLast(_)).getOrElse(0))
}
//Show last element in the list, most current
def averageStockLevel (stock: String): (String, Int) = {
(stock, mapdata.get (stock).map(average(_).toInt).getOrElse(0))
}
}
答案 0 :(得分：0)
被修改
根据评论的要求。
＆＃34;例如＆＃34; SK1＆＃34;然后是另一个值，＆＃34; SK2＆＃34;这将比较2个列表并返回更大的＆＃34;
def largestList(a: String, b: String): Option[List[Int]] = {
(map.get(a), map.get(b)) match {
case (Some(alist), Some(blist)) => Some(List(alist, blist).maxBy(_.size))
case _ => None
}
}
val map = Map("stock1" -> List(1, 2), "stock2" -> List(3, 4, 5))
scala> largestList("stock1", "stock2")
res24: Option[List[Int]] = Some(List(3, 4, 5))
旧答案
我假设给定地图Map[String, List[Int]]您想使用值中的值（List [Int]）搜索地图
例如，如果您想获取包含两个数字1,2的值的键值对，则执行
map.filter { case (k, v) => v.exists(Set(1, 2)) }
Scala REPL
scala> val map = Map("stock1" -> List(1, 2), "stock2" -> List(3, 4, 5))
map: Map[String, List[Int]] = Map("stock1" -> List(1, 2), "stock2" -> List(3, 4, 5))
scala> map.filter { case (k, v) => v.exists(Set(3, 4))}
res20: Map[String, List[Int]] = Map("stock2" -> List(3, 4, 5))