Scala题目

package homeWork

import org.junit.{Before, Test}

import scala.io.{BufferedSource, Source}

class teacherAnswer {
  var stu: List[Students] = _
  var sco: List[Score] = _
  var sub: List[Subject] = _


  var stuInfoMap: Map[String, String] = _
  var subNameMap: Map[String, String] = _
  var subScoreMap: Map[String, Int] = _


  // 分别定义学生、分数、科目数据的样例类
  case class Students(id: String, name: String, age: Int, gender: String, clazz: String)

  case class Score(id: String, subject_id: String, score: Int)

  case class Subject(subject_id: String, subject_name: String, subject_score: Int)

  // 基于id的List 关联三份数据 最终输出 [学号,姓名，班级，科目，分数]
  def printAndFilterWithIds(ids: List[String]): Unit = {
    // 基于分数数据结合两个Map进行关联
    sco
      .filter(s => ids.contains(s.id))
      .map(s => {
        val nameAndClazz: String = stuInfoMap.getOrElse(s.id, "无此学生")
        val subjectName: String = subNameMap.getOrElse(s.subject_id, "无此科目")

        s"${s.id},$nameAndClazz,$subjectName,${s.score}"
      })
      .foreach(println)
  }

  // 加载数据
  @Before
  def loadData(): Unit = {
    // 读数据并且将每条数据转换成对应的样例类对象然后构成List
    val stuBS: BufferedSource = Source.fromFile("data/students.txt")
    stu = stuBS
      .getLines()
      .toList
      .map(s => {
        val splits = s.split(",")
        val id: String = splits(0)
        val name: String = splits(1)
        val age: Int = splits(2).toInt
        val gender: String = splits(3)
        val clazz: String = splits(4)
        Students(id, name, age, gender, clazz)
      })

    // 以id作为key，name和clazz作为value构建Map
    stuInfoMap = stu
      .map(s => (s.id, s.name + "," + s.clazz))
      .toMap

    val scoBS: BufferedSource = Source.fromFile("data/score.txt")
    sco = scoBS
      .getLines()
      .toList
      .map(s => {
        val splits = s.split(",")
        val id: String = splits(0)
        val subject_id: String = splits(1)
        val score: Int = splits(2).toInt
        Score(id, subject_id, score)
      })

    val subBS: BufferedSource = Source.fromFile("data/subject.txt")
    sub = subBS
      .getLines()
      .toList
      .map(s => {
        val splits = s.split(",")
        val subject_id: String = splits(0)
        val subject_name: String = splits(1)
        val subject_score: Int = splits(2).toInt
        Subject(subject_id, subject_name, subject_score)
      })

    // 以科目id作为key，科目名作为value构建Map
    subNameMap = sub
      .map(s => (s.subject_id, s.subject_name))
      .toMap
    // 以科目id作为key，科目总分作为value构建Map
    subScoreMap = sub
      .map(s => (s.subject_id, s.subject_score))
      .toMap

    stuBS.close()
    scoBS.close()
    subBS.close()
  }

  @Test
  // 将加载的数据打印
  def printData(): Unit = {
    stu.take(10).foreach(println)
    sco.take(10).foreach(println)
    sub.take(10).foreach(println)
  }

  @Test
  // 统计班级人数"
  def clazzCount(): Unit = {
    stu
      // List在groupBy之后会返回一个Map
      .groupBy(s => s.clazz)
      .map(kv => kv._1 + "," + kv._2.size)
      .foreach(println)
  }

  @Test
  // 统计学生的总分 [学号,学生姓名,学生年龄,总分]
  def stuSumScore(): Unit = {
    // 统计每个学生的总分
    val stuSumScoreMap: Map[String, Int] = sco
      .groupBy(s => s.id)
      // 当List在groupBy之后再调用map方法，如果map方法返回的是一个二元组，则最终会得到一个Map
      .map(kv => (kv._1, kv._2.map(_.score).sum))

    // 依次遍历每一条学生的数据，通过id从stuSumScoreMap中获取学生总分
    stu
      .map(s => {
        // 获取总分
        val sumScore: Int = stuSumScoreMap.getOrElse(s.id, 0)
        s"${s.id},${s.name},${s.age},$sumScore"
      })
      .foreach(println)
  }

  @Test
  // 1、统计年级排名前十学生各科的分数 [学号,姓名，班级，科目，分数]
  def question01(): Unit = {
    // 找出排名前10学生的id
    val top10Ids: List[String] = sco
      .groupBy(s => s.id)
      .map(kv => (kv._1, kv._2.map(_.score).sum))
      .toList
      .sortBy(kv => -kv._2)
      .take(10)
      .map(_._1)

    printAndFilterWithIds(top10Ids)
  }

  @Test
  // 2、统计总分大于年级平均分的学生 [学号，姓名，班级，总分]
  def question02(): Unit = {
    // 统计年级的平均分 372.704
    val avgSumScore: Double = sco.map(_.score).sum / stu.size.toDouble

    // 统计每个学生的总分
    sco
      .groupBy(_.id)
      .map(kv => (kv._1, kv._2.map(_.score).sum))
      // 过滤出总分大于平均分的学生
      .filter(kv => kv._2 > avgSumScore)
      // 通过id与学生数据进行关联
      .map(kv => {
        val nameAndClazz: String = stuInfoMap.getOrElse(kv._1, "无此学生信息")
        s"${kv._1},$nameAndClazz,${kv._2}"
      })
      .foreach(println)

  }

  @Test
  // 3、统计每科都及格的学生 [学号，姓名，班级，科目，分数]
  def question03(): Unit = {
    // 关联分数和学科的数据
    val ids: List[String] = sco
      .filter(s => s.score >= subScoreMap.getOrElse(s.subject_id, 0) * 0.6)
      // 统计每个学生及格的科目数
      .groupBy(_.id)
      .map(kv => (kv._1, kv._2.size))
      .filter(kv => kv._2 == 6)
      .keys
      .toList

    printAndFilterWithIds(ids)

  }

  @Test
  // 4、统计每个班级的前三名 [学号，姓名，班级，分数]
  def question04(): Unit = {
    // 统计学生总分
    sco
      .groupBy(_.id)
      .map(kv => (kv._1, kv._2.map(_.score).sum))
      // 基于id从学生信息Map中获取学生名字以及班级
      .map(kv => {
        val nameAndClazz: String = stuInfoMap.getOrElse(kv._1, "无此学生信息")
        val splits = nameAndClazz.split(",")
        val name: String = splits(0)
        val clazz: String = splits(1)
        (kv._1, name, clazz, kv._2)
      })
      .groupBy(_._3)
      .flatMap(kv =>
        kv._2.toList.sortBy(-_._4).take(3)
      )
      .foreach(println)

  }

  @Test
  // 5、统计偏科最严重的前100名学生  [学号，姓名，班级，科目，分数]
  def question05(): Unit = {
    val ids:List[String] = sco
      // 对数据进行归一化处理
      .map(s => (s.id, s.subject_id, s.score * 100.toDouble / subScoreMap.getOrElse(s.subject_id, 0)))
      .groupBy(_._1)
      .map(kv => {
        val id: String = kv._1
        val scoreList: List[(String, String, Double)] = kv._2
        // 计算平均分
        val stuAvgScore: Double = scoreList.map(_._3).sum / scoreList.size
        // 计算方差
        val variance: Double = scoreList.map(t3 => Math.pow(t3._3 - stuAvgScore, 2)).sum / scoreList.size
        (id, variance)
      })
      .toList
      .sortBy(-_._2)
      .take(100)
      .map(_._1)

    printAndFilterWithIds(ids)
  }

}